RISC-V: 'Zfa' extension is now ratified

Since this extension is ratified, it now has the version number 1.0.

Reference:
<https://github.com/riscv/riscv-isa-manual/pull/1096>

gcc/ChangeLog:

	* common/config/riscv/riscv-common.cc (riscv_ext_version_table):
	Change version number of the 'Zfa' extension to 1.0.