mn10300: fix "pull clearing RESTORE_SIGMASK into block_sigmask()" fallout

mn10300: fix "pull clearing RESTORE_SIGMASK into block_sigmask()" fallout

Commit a610d6e672d6 ("pull clearing RESTORE_SIGMASK into
block_sigmask()") caused:

  arch/mn10300/kernel/signal.c: In function 'handle_signal':
  arch/mn10300/kernel/signal.c:462:3: warning: 'return' with no value, in function returning non-void [-Wreturn-type]

Add the missing return values, and restore the indentation while we're
at it.

Signed-off-by: Geert Uytterhoeven <[email protected]>
Cc: Al Viro <[email protected]>
Cc: David Howells <[email protected]>
Cc: Koichi Yasutake <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>