MIPS: inst.h: Fix some instruction descriptions

MIPS: inst.h: Fix some instruction descriptions

Fix the description of the microMIPS NOP16 encoding or MM_NOP16, which
is not equivalent to the MIPS16 NOP instruction.  This is 0x0c00 and
represents the microMIPS `MOVE16 $0, $0' operation, whereas MIPS16 NOP
is encoded as 0x6500, representing `MOVE $0, $16'.

Also fix a typo in `mm_fp0_format' description.

Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12177/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>