RISC-V: Add 'Smstateen' extension and its CSRs

RISC-V: Add 'Smstateen' extension and its CSRs

This commit adds State Enable Extension (Smstateen) and its CSRs.

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_supported_std_s_ext): Add 'Smstateen'
	extension to valid 'S' extension list.

gas/ChangeLog:

	* config/tc-riscv.c (enum riscv_csr_class): Add CSR classes for
	'Smstateen' extension. (riscv_csr_address): Add handling for
	new CSR classes.
	* testsuite/gas/riscv/csr-dw-regnums.s: Add new CSRs.
	* testsuite/gas/riscv/csr-dw-regnums.d: Likewise.
	* testsuite/gas/riscv/csr.s: Add new CSRs.
	* testsuite/gas/riscv/csr-version-1p9p1.d: Likewise.
	* testsuite/gas/riscv/csr-version-1p9p1.l: Likewise.
	* testsuite/gas/riscv/csr-version-1p10.d: Likewise.
	* testsuite/gas/riscv/csr-version-1p10.l: Likewise.
	* testsuite/gas/riscv/csr-version-1p11.d: Likewise.
	* testsuite/gas/riscv/csr-version-1p11.l: Likewise.
	* testsuite/gas/riscv/csr-version-1p12.d: Likewise.
	* testsuite/gas/riscv/csr-version-1p12.l: Likewise.

include/ChangeLog:

	* opcode/riscv-opc.h (CSR_MSTATEEN0, CSR_MSTATEEN1,
	CSR_MSTATEEN2, CSR_MSTATEEN3, CSR_SSTATEEN0, CSR_SSTATEEN1,
	CSR_SSTATEEN2, CSR_SSTATEEN3, CSR_HSTATEEN0, CSR_HSTATEEN1,
	CSR_HSTATEEN2, CSR_HSTATEEN3, CSR_MSTATEEN0H, CSR_MSTATEEN1H,
	CSR_MSTATEEN2H, CSR_MSTATEEN3H, CSR_HSTATEEN0H, CSR_HSTATEEN1H,
	CSR_HSTATEEN2H, CSR_HSTATEEN3H): New CSR macros.