spi: imx: remove CLK calculation and check for target mode

spi: imx: remove CLK calculation and check for target mode

In target mode, the clock signal is controlled by the master. Target does
not need to check, calculate and configure the clock frequency division.
The target can directly use the root clock to sample the SCL signal.

Therefore, remove check, calculation and frequency division function of
the clock for target mode.

Signed-off-by: Carlos Song <carlos.song@nxp.com>
Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20251024055211.408440-1-carlos.song@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>