[AArch64] Allow MOVPRFX to be used with FMOV

[AArch64] Allow MOVPRFX to be used with FMOV

The entry for the FMOV alias of FCPY was missing C_SCAN_MOVPRFX.
(The entry for FCPY itself was OK.)

This was the only /m-predicated instruction I could see that was
missing the flag.

2019-07-02  Richard Sandiford  <richard.sandiford@arm.com>

opcodes/
	* aarch64-tbl.h (aarch64_opcode): Set C_SCAN_MOVPRFX for the
	SVE FMOV alias of FCPY.

gas/
	* testsuite/gas/aarch64/sve-movprfx_27.s,
	* testsuite/gas/aarch64/sve-movprfx_27.d: New test.