RISC-V: Add Zba, Zbs extension probing

RISC-V: Add Zba, Zbs extension probing

Add the Zba address bit manipulation extension and Zbs single bit
instructions extension into those the kernel is aware of and maintains
in its riscv_isa bitmap.

Signed-off-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Link: https://lore.kernel.org/r/20230509182504.2997252-2-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>