mips: ip22: Reword PANICED to PANICKED and remove useless header

Many other place in the kernel prefer the latter, so let's keep
it consistent in MIPS code as well. Also, removes a useless header.

Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>