sparc: fix sparse warnings in traps_32.c

o add decalrations to entry.h for functions only used from assembler
o add declaratiosn to kernel.h for functions only used from .c
o removed unused functions/extern declarations

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