RISC-V: Update 'Zfa' extension version

Because the 'Zfa' extension has a version number of 1.0
(not 0.1). This commit updates the number.

bfd/ChangeLog:

            * elfxx-riscv.c (riscv_supported_std_z_ext): Update the version
            number of the 'Zfa' extension since it's ratified.