clk: COMMON_CLK_RPMI should depend on RISCV

The RISC-V platform management interface (RPMI) is only available on
RISC-V platforms.  Hence add a dependency on RISCV, to prevent asking
the user about this driver when configuring a kernel for a different
architecture.

Fixes: 5ba9f520f4 ("clk: Add clock driver for the RISC-V RPMI clock service group")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Paul Walmsley <pjw@kernel.org>

drivers/clk/Kconfig

@@ -503,6 +503,7 @@ config COMMON_CLK_SP7021
 
 config COMMON_CLK_RPMI
 	tristate "Clock driver based on RISC-V RPMI"
+	depends on RISCV || COMPILE_TEST
 	depends on MAILBOX
 	default RISCV
 	help