RISC-V: defconfig: enable clocks, serial console

Enable PRCI clock driver and serial console by default, so the default
upstream defconfig is bootable to a serial console.
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/configs/defconfig

@@ -49,6 +49,8 @@ CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_OF_PLATFORM=y
 CONFIG_SERIAL_EARLYCON_RISCV_SBI=y
+CONFIG_SERIAL_SIFIVE=y
+CONFIG_SERIAL_SIFIVE_CONSOLE=y
 CONFIG_HVC_RISCV_SBI=y
 # CONFIG_PTP_1588_CLOCK is not set
 CONFIG_DRM=y
@@ -64,6 +66,8 @@ CONFIG_USB_OHCI_HCD_PLATFORM=y
 CONFIG_USB_STORAGE=y
 CONFIG_USB_UAS=y
 CONFIG_VIRTIO_MMIO=y
+CONFIG_CLK_SIFIVE=y
+CONFIG_CLK_SIFIVE_FU540_PRCI=y
 CONFIG_SIFIVE_PLIC=y
 CONFIG_EXT4_FS=y
 CONFIG_EXT4_FS_POSIX_ACL=y