spi: spi-nxp-fspi: add extra delay after dll locked

spi: spi-nxp-fspi: add extra delay after dll locked

Due to the erratum ERR050272, the DLL lock status register STS2
[xREFLOCK, xSLVLOCK] bit may indicate DLL is locked before DLL is
actually locked. Add an extra 4us delay as a workaround.

refer to ERR050272, on Page 20.
https://www.nxp.com/docs/en/errata/IMX8_1N94W.pdf

Fixes: 99d822b3adc4 ("spi: spi-nxp-fspi: use DLL calibration when clock rate > 100MHz")
Signed-off-by: Han Xu <han.xu@nxp.com>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Link: https://patch.msgid.link/20250922-fspi-fix-v1-2-ff4315359d31@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>