RISC-V: Enable ztso tests on rv32

RISC-V: Enable ztso tests on rv32

This patch transitions the ztso testcases to use the testsuite infrastructure,
enabling the tests on both rv64 and rv32 targets.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/amo-table-ztso-amo-add-1.c: Add Ztso extension to
	dg-options for dg-do compile.
	* gcc.target/riscv/amo-table-ztso-amo-add-2.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-amo-add-3.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-amo-add-4.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-amo-add-5.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-compare-exchange-1.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-compare-exchange-2.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-compare-exchange-3.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-compare-exchange-4.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-compare-exchange-5.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-compare-exchange-6.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-compare-exchange-7.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-fence-1.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-fence-2.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-fence-3.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-fence-4.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-fence-5.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-load-1.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-load-2.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-load-3.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-store-1.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-store-2.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-store-3.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-subword-amo-add-1.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-subword-amo-add-2.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-subword-amo-add-3.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-subword-amo-add-4.c: Ditto.
	* gcc.target/riscv/amo-table-ztso-subword-amo-add-5.c: Ditto.
	* lib/target-supports.exp: Add testing infrastructure to require the
	Ztso extension or add it to an existing -march.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>
(cherry picked from commit ea2e7bf80b8deead064d9b54c3caa852dfe009b3)