arm64: dts: rockchip: increase spi-max-frequency of nor flash for roc-rk3399-pc

Increase the spi-max-frequency of nor flash from 10Mhz to 30Mhz,this improves the
flash raw write speed by 0.9 MB/s to 1.6MB/s and the time taken to write is
get reduced from 36 seconds to 20 seconds.

Signed-off-by: Manoj Sai <abbaraju.manojsai@amarulasolutions.com>
Link: https://lore.kernel.org/r/20221124072714.450223-1-abbaraju.manojsai@amarulasolutions.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>