MIPS: Normalise code flow in the CpU exception handler

Changes applied to `do_cpu' over time reduced the use of the SIGILL
issued with `force_sig' at the end to a single CU3 case only in the
switch statement there.  Move that `force_sig' call over to right where
required then and toss out the pile of gotos now not needed to skip over
the call, replacing them with regular breaks out of the switch.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9683/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>