[MIPS] kgdb: Do not call fixup_exception

kgdb_mips_notify is called on IBE/DBE/FPE/BP/TRAP/RI exception.  None
of them need fixup.  And doing fixup for a breakpoint exception will
confuse gdb.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>