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