Rename some register statics by prefixing their names with arch.

Rename some register statics by prefixing their names with arch.

This makes it easier to grep for them.

* syscall.c: Make IA64's r8, r10 global variables static.
Rename variables:
r8,r10 -> ia64_r8,ia64_r10.
d0 -> m68k_d0.
a3 -> alpha_a3.
r28 -> hppa_r28.
r9 -> sh64_r9.
r10 -> cris_r10.
r3 -> microblaze_r3.
(get_scno): Use new variable names.
(syscall_fixup_on_sysenter): Likewise.
(get_syscall_result): Likewise.
(get_error): Likewise.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>