riscv: Add AIA extension support (Smaia, Ssaia)

This commit adds the AIA extensions (Smaia and Ssaia) CSRs.

bfd/ChangeLog:

	* elfxx-riscv.c: Add 'smaia' and 'ssaia' to the list
	of known standard extensions.

gas/ChangeLog:

	* config/tc-riscv.c (enum riscv_csr_class):
	(riscv_csr_address): Add CSR classes for Smaia/Ssaia.
	* testsuite/gas/riscv/csr-dw-regnums.d: Add new CSRs.
	* testsuite/gas/riscv/csr-dw-regnums.s: 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.
	* testsuite/gas/riscv/csr-version-1p9p1.d: Likewise.
	* testsuite/gas/riscv/csr-version-1p9p1.l: Likewise.
	* testsuite/gas/riscv/csr.s: Likewise.

include/ChangeLog:

	* opcode/riscv-opc.h (CSR_MISELECT): New CSR macro.
	(CSR_MIREG): Likewise.
	(CSR_MTOPEI): Likewise.
	(CSR_MTOPI): Likewise.
	(CSR_MVIEN): Likewise.
	(CSR_MVIP): Likewise.
	(CSR_MIDELEGH): Likewise.
	(CSR_MIEH): Likewise.
	(CSR_MVIENH): Likewise.
	(CSR_MVIPH): Likewise.
	(CSR_MIPH): Likewise.
	(CSR_SISELECT): Likewise.
	(CSR_SIREG): Likewise.
	(CSR_STOPEI): Likewise.
	(CSR_STOPI): Likewise.
	(CSR_SIEH): Likewise.
	(CSR_SIPH): Likewise.
	(CSR_HVIEN): Likewise.
	(CSR_HVICTL): Likewise.
	(CSR_HVIPRIO1): Likewise.
	(CSR_HVIPRIO2): Likewise.
	(CSR_VSISELECT): Likewise.
	(CSR_VSIREG): Likewise.
	(CSR_VSTOPEI): Likewise.
	(CSR_VSTOPI): Likewise.
	(CSR_HIDELEGH): Likewise.
	(CSR_HVIENH): Likewise.
	(CSR_HVIPH): Likewise.
	(CSR_HVIPRIO1H): Likewise.
	(CSR_HVIPRIO2H): Likewise.
	(CSR_VSIEH): Likewise.
	(CSR_VSIPH): Likewise.
	(DECLARE_CSR): Add CSRs for Smaia and Ssaia.

Changes for v3:
- Imply ssaia for smaia
- Imply zicsr for ssaia (and transitively smaia)
- Move hypervisor CSRs to Ssaia+H
- Rebase on upstream/master

Changes for v2:
- Add hypervisor and VS CSRs
- Fix whitespace issue

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>