[SPARC64]: More sparse warning fixes in process.c

arch/sparc64/kernel/process.c:504:17: warning: symbol 'sparc_do_fork' was not declared. Should it be static?
arch/sparc64/kernel/process.c:655:5: warning: symbol 'dump_fpu' was not declared. Should it be static?
arch/sparc64/kernel/process.c:708:16: warning: symbol 'sparc_execve' was not declared. Should it be static?

Signed-off-by: David S. Miller <davem@davemloft.net>