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.