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: 99d822b ("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>

Author: hanxu-nxp

drivers/spi/spi-nxp-fspi.c

@@ -721,6 +721,12 @@ static void nxp_fspi_dll_calibration(struct nxp_fspi *f)
 				   0, POLL_TOUT, true);
 	if (ret)
 		dev_warn(f->dev, "DLL lock failed, please fix it!\n");
+
+	/*
+	 * For ERR050272, DLL lock status bit is not accurate,
+	 * wait for 4us more as a workaround.
+	 */
+	udelay(4);
 }
 
 /*