lib: sbi: Use the official extension name for AIA M-mode CSRs

The arch review of AIA spec is completed and we now have official
extension names for AIA: Smaia (M-mode AIA CSRs) and Ssaia (S-mode
AIA CSRs).

Refer, section 1.6 of the latest AIA v0.3.1 stable specification at
https://github.com/riscv/riscv-aia/releases/download/0.3.1-draft.32/riscv-interrupts-032.pdf

)

Based on above, we update generic library to use "Smaia" extension
name for AIA M-mode CSRs.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>