sparc64: Fix prototype warnings in traps_64.c

sparc64: Fix prototype warnings in traps_64.c

Fix the following warnings:
arch/sparc/kernel/traps_64.c:253:6: warning: no previous prototype for ‘is_no_fault_exception’
arch/sparc/kernel/traps_64.c:2035:6: warning: no previous prototype for ‘do_mcd_err’
rch/sparc/kernel/traps_64.c:2153:6: warning: no previous prototype for ‘sun4v_nonresum_error_user_handled’

In all cases make the function static as there were no users outside
traps_64.c

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: David S. Miller <davem@davemloft.net>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Tested-by: Andreas Larsson <andreas@gaisler.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20240330-sparc64-warnings-v1-2-37201023ee2f@ravnborg.org
Signed-off-by: Andreas Larsson <andreas@gaisler.com>