RISC-V: convert new selectors of RISCV_ALTERNATIVE to dependencies

for-next contains two additional extensions that select
RISCV_ALTERNATIVE. RISCV_ALTERNATIVE no longer needs to be selected by
individual config options as it is now selected for !XIP_KERNEL builds
by the top level RISCV option.
These extensions rely on the alternative framework, so convert the
"select"s to "depends on"s instead.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20230324121240.3594777-1-conor.dooley@microchip.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Kconfig

@@ -402,8 +402,8 @@ config RISCV_ISA_C
 config RISCV_ISA_SVNAPOT
 	bool "SVNAPOT extension support"
 	depends on 64BIT && MMU
+	depends on RISCV_ALTERNATIVE
 	default y
-	select RISCV_ALTERNATIVE
 	help
 	  Allow kernel to detect the SVNAPOT ISA-extension dynamically at boot
 	  time and enable its usage.
@@ -478,8 +478,8 @@ config RISCV_ISA_ZICBOM
 
 config RISCV_ISA_ZICBOZ
 	bool "Zicboz extension support for faster zeroing of memory"
-	depends on !XIP_KERNEL && MMU
-	select RISCV_ALTERNATIVE
+	depends on MMU
+	depends on RISCV_ALTERNATIVE
 	default y
 	help
 	   Enable the use of the ZICBOZ extension (cbo.zero instruction)