Prevent undefined FMOV instructions being accepted by the AArch64 assembler.

Prevent undefined FMOV instructions being accepted by the AArch64 assembler.

    Detect illegal FMOV instructions that changes the size from 32 bits to 64
    bits and vice versa. Add tests for these and other undefined FMOV
    instructions.

        PR 20319
gas     * testsuite/gas/aarch64/illegal-3.s: Test if unallocated FMOV encodings
        are detected as undefined.
        * testsuite/gas/aarch64/illegal-3.d: Likewise.
        * testsuite/gas/aarch64/illegal.s: Test if FMOV instructions that are
        changing the size from 32 bits to 64 bits and vice versa trigger an
        error.
        * testsuite/gas/aarch64/illegal.l: Likewise.

opcodes * aarch64-tbl.h: Introduce QL_INT2FP_FMOV and QL_FP2INT_FMOV.
        (aarch64_opcode_table) : Use QL_INT2FP_FMOV and QL_FP2INT_FMOV.