arc/opcodes/nps400: Fix some instruction masks

arc/opcodes/nps400: Fix some instruction masks

A few masks were incorrect, there were opcode bits that lives outside of
the instruction mask, the effected instructions are decode1, zncv, and
efabgt.

Previously these instructions would assemble and disassemble correctly,
and a correctly encoded binary should behave no differently.  The only
difference would be seen in a few incorrectly encoded binaries,
previously these would have decoded to the above instructions, while now
they will not.

opcodes/ChangeLog:

	* arc-nps400-tbl.h: Fix some instruction masks.