MIPS: traps: print Exception Code in __show_regs()

Print Exception Code when printing the Cause register.

Signed-off-by: Petri Gynther <pgynther@google.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9998/


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