RISC-V: Support Zca/f/d extensions.

RISC-V: Support Zca/f/d extensions.

This patch add Zca/f/d extensions support, since all ZC*
extensions will imply Zca extension, just enabled compress
feature when Zca extension is available.

Co-Authored by: Charlie Keaney <charlie.keaney@embecosm.com>
Co-Authored by: Mary Bennett <mary.bennett@embecosm.com>
Co-Authored by: Nandni Jamnadas <nandni.jamnadas@embecosm.com>
Co-Authored by: Sinan Lin <sinan.lin@linux.alibaba.com>
Co-Authored by: Simon Cook <simon.cook@embecosm.com>
Co-Authored by: Shihua Liao <shihua@iscas.ac.cn>
Co-Authored by: Yulong Shi <yulong@iscas.ac.cn>

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_multi_subset_supports): New extensions.
	(riscv_multi_subset_supports_ext): Ditto.

gas/ChangeLog:

	* config/tc-riscv.c (riscv_set_arch): Extend compress check.
	* testsuite/gas/riscv/zca.d: New test.
	* testsuite/gas/riscv/zca.s: New test.
	* testsuite/gas/riscv/zcd.d: New test.
	* testsuite/gas/riscv/zcd.s: New test.
	* testsuite/gas/riscv/zcf.d: New test.
	* testsuite/gas/riscv/zcf.s: New test.