RISC-V: fix ordering of Zbb extension

RISC-V: fix ordering of Zbb extension

As Andrew reported,
    Zb* comes after Zi* according 27.11 "Subset Naming Convention"
so fix the ordering accordingly.

Reported-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230208225328.1636017-2-heiko@sntech.de
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>