[ARM] Fix the decoding of indexed element VCMLA instruction

Bit 24 of the indexed element vcmla decode mask was incorrectly
left unset.  This could cause incorrect disassembly of some
currently undefined instructions as vcmla.

Rotatation immediates were not printed correctly in the disassembly
(could print 170 and 280 instead of 180 and 270).

opcodes/
	* arm-dis.c (coprocessor_opcodes): Fix vcmla mask and disassembly.

gas/
	* testsuite/gas/arm/armv8_3-a-simd.s: Add vcmla tests.
	* testsuite/gas/arm/armv8_3-a-simd.d: Update.