ia64: add __NR_old_getpagesize in uapi header file

sys_getpagesize entry is present in kernel/entry.S file to
support for old user interface. So we need to add an uapi
entry too.

Add __NR_old_getpagesize in uapi/asm/unistd.h in order to
not break old user space as it is reserved for backwards
compatibility with old __NR_getpagesize.

Signed-off-by: Firoz Khan <firoz.khan@linaro.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>