MIPS: drop unused pic32.h header

All users of the MIPS pic32.h asm header have been migrated to
linux/platform_data/pic32.h, so let's go ahead and drop the unused asm
variant.

Signed-off-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: masneyb