riscv: Remove MMU dependency from Zbb and Zicboz

The Zbb and Zicboz ISA extensions have no dependency on an MMU and are
equally useful on NOMMU kernels.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240227003630.3634533-4-samuel.holland@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: SiFiveHolland

arch/riscv/Kconfig

@@ -581,7 +581,6 @@ config TOOLCHAIN_HAS_ZBB
 config RISCV_ISA_ZBB
 	bool "Zbb extension support for bit manipulation instructions"
 	depends on TOOLCHAIN_HAS_ZBB
-	depends on MMU
 	depends on RISCV_ALTERNATIVE
 	default y
 	help
@@ -613,7 +612,6 @@ config RISCV_ISA_ZICBOM
 
 config RISCV_ISA_ZICBOZ
 	bool "Zicboz extension support for faster zeroing of memory"
-	depends on MMU
 	depends on RISCV_ALTERNATIVE
 	default y
 	help