sparc32: fix sparse warnings in sys_sparc_32.c

Fix following warnings:
sys_sparc_32.c:32:26: warning: symbol 'sys_getpagesize' was not declared. Should it be static?
sys_sparc_32.c:71:16: warning: symbol 'sparc_pipe' was not declared. Should it be static?
sys_sparc_32.c:96:26: warning: symbol 'sys_mmap2' was not declared. Should it be static?
sys_sparc_32.c:106:26: warning: symbol 'sys_mmap' was not declared. Should it be static?
sys_sparc_32.c:114:6: warning: symbol 'sparc_remap_file_pages' was not declared. Should it be static?
sys_sparc_32.c:127:1: warning: symbol 'c_sys_nis_syscall' was not declared. Should it be static?
sys_sparc_32.c:144:1: warning: symbol 'sparc_breakpoint' was not declared. Should it be static?
sys_sparc_32.c:200:16: warning: symbol 'sys_getdomainname' was not declared. Should it be static?

Adapt systbls.h for use by both sparc32 + sparc64.
In the process modify the return type of a few functions.

Change return type from unsigned long to long:
sys_mmap2()
sys_mmap()

Change return type from int to long:
sparc_pipe()
sys_getdomainname()

The changed return type was done to align with sparc64.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>