arm: opcodes: remove Maverick disassembly.

Remove the patterns to match Maverick co-processor instructions from
the disassembly tables.

This required fixing a couple of tests in the assembler testsuite
where we, probably incorrectly, disassembled generic co-processor
instructions as a Maverick instruction (it particularly made no sense
to do this for Armv6t2 in Thumb state).