riscv: sbi: remove useless parenthesis

A few parenthesis in check for SBI version/extension were useless,
remove them.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20250523101932.1594077-3-cleger@rivosinc.com


Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>