RISC-V: Fix parsing of Zic* extensions

RISC-V: Fix parsing of Zic* extensions

The extension parsing table entries for a range of Zic* extensions
does not match the mask definition in riscv.opt.
This results in broken TARGET_ZIC* macros, because the values of
riscv_zi_subext and riscv_zicmo_subext are set wrong.

This patch fixes this by moving Zic64b into riscv_zicmo_subext
and all other affected Zic* extensions to riscv_zi_subext.

gcc/ChangeLog:

	* common/config/riscv/riscv-common.cc: Move ziccamoa, ziccif,
	zicclsm, and ziccrse into riscv_zi_subext.
	* config/riscv/riscv.opt: Define MASK_ZIC64B for
	riscv_ziccmo_subext.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>