openrisc: signal: Fix sparse address space warnings

The __user annotations in signal.c were mostly missing.  The missing
annotations caused the warnings listed below.  This patch fixes them up
by adding the __user annotations.

arch/openrisc/kernel/signal.c:71:38: warning: incorrect type in initializer (different address spaces)
arch/openrisc/kernel/signal.c:71:38:    expected struct rt_sigframe *frame
arch/openrisc/kernel/signal.c:71:38:    got struct rt_sigframe [noderef] __user *
arch/openrisc/kernel/signal.c:82:14: warning: incorrect type in argument 1 (different address spaces)
arch/openrisc/kernel/signal.c:82:14:    expected void const volatile [noderef] __user *
arch/openrisc/kernel/signal.c:82:14:    got struct rt_sigframe *frame
arch/openrisc/kernel/signal.c:84:37: warning: incorrect type in argument 2 (different address spaces)
arch/openrisc/kernel/signal.c:84:37:    expected void const [noderef] __user *from
arch/openrisc/kernel/signal.c:84:37:    got struct sigset_t *
arch/openrisc/kernel/signal.c:89:39: warning: incorrect type in argument 2 (different address spaces)
arch/openrisc/kernel/signal.c:89:39:    expected struct sigcontext [noderef] __user *sc
arch/openrisc/kernel/signal.c:89:39:    got struct sigcontext *
arch/openrisc/kernel/signal.c:92:31: warning: incorrect type in argument 1 (different address spaces)
arch/openrisc/kernel/signal.c:92:31:    expected struct sigaltstack const [noderef] [usertype] __user *
arch/openrisc/kernel/signal.c:92:31:    got struct sigaltstack *
arch/openrisc/kernel/signal.c:158:15: warning: incorrect type in assignment (different address spaces)
arch/openrisc/kernel/signal.c:158:15:    expected struct rt_sigframe *frame
arch/openrisc/kernel/signal.c:158:15:    got void [noderef] __user *
arch/openrisc/kernel/signal.c:160:14: warning: incorrect type in argument 1 (different address spaces)
arch/openrisc/kernel/signal.c:160:14:    expected void const volatile [noderef] __user *
arch/openrisc/kernel/signal.c:160:14:    got struct rt_sigframe *frame
arch/openrisc/kernel/signal.c:165:46: warning: incorrect type in argument 1 (different address spaces)
arch/openrisc/kernel/signal.c:165:46:    expected struct siginfo [noderef] [usertype] __user *to
arch/openrisc/kernel/signal.c:165:46:    got struct siginfo *
arch/openrisc/kernel/signal.c:170:33: warning: incorrect type in argument 1 (different address spaces)
arch/openrisc/kernel/signal.c:170:33:    expected struct sigaltstack [noderef] [usertype] __user *
arch/openrisc/kernel/signal.c:170:33:    got struct sigaltstack *
arch/openrisc/kernel/signal.c:171:40: warning: incorrect type in argument 2 (different address spaces)
arch/openrisc/kernel/signal.c:171:40:    expected struct sigcontext [noderef] __user *sc
arch/openrisc/kernel/signal.c:171:40:    got struct sigcontext *
arch/openrisc/kernel/signal.c:173:32: warning: incorrect type in argument 1 (different address spaces)
arch/openrisc/kernel/signal.c:173:32:    expected void [noderef] __user *to
arch/openrisc/kernel/signal.c:173:32:    got struct sigset_t *

Signed-off-by: Stafford Horne <shorne@gmail.com>
Reviewed-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>