LPSPI transfer max speed is half of the root clock.
Increase the root clock speed to support faster data transmission.

And update the parent clock of all i2c/spi with IMX8ULP_CLK_FROSC_DIV2
which could produce accurate clock for i2c/spi usage.
Reviewed-by: Haibo Chen <haibo.chen@nxp.com>
Reviewed-by: Jun Li <jun.li@nxp.com>
Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>