sh: make copy_to/from_user() static inline

This patch changes copy_from_user() and copy_to_user() from macros
into static inline functions. This way we can use them as function
pointers. Also unify the 64 bit and 32 bit versions.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>