riscv: select SiFive platform drivers with SOC_SIFIVE

On selection of SOC_SIFIVE select the corresponding platform drivers.
Signed-off-by: Loys Ollivier <lollivier@baylibre.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/Kconfig.socs

@@ -2,6 +2,11 @@ menu "SoC selection"
 
 config SOC_SIFIVE
        bool "SiFive SoCs"
+       select SERIAL_SIFIVE
+       select SERIAL_SIFIVE_CONSOLE
+       select CLK_SIFIVE
+       select CLK_SIFIVE_FU540_PRCI
+       select SIFIVE_PLIC
        help
          This enables support for SiFive SoC platform hardware.