RISC-V/zfh: Added big endian testcase for .float16 directive.

gas/
    * testsuite/gas/riscv/extended/extended.exp: Updated.
    * testsuite/gas/riscv/extended/float16.s: Minor fix for sNaNh.
    * testsuite/gas/riscv/extended/float16-le.d: Updated and renamed
    from float16.d.
    * testsuite/gas/riscv/extended/float16-be.d: New testcase.
4 files changed