RISC-V: Update ratified 'Ztso' extension version

Because the 'Ztso' extension is now ratified, it 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 'Ztso' extension since it's ratified.