spi: spi-nxp-fspi: few fix for flexspi

spi: spi-nxp-fspi: few fix for flexspi

Merge series from Haibo Chen <haibo.chen@nxp.com>:

PATCH 1: different operations maybe require different max frequency, so
         add flexspi to handle such case, re-config the clock rate when
	 new coming operation require new clock frequency.
Patch 2: add workaround for erratum ERR050272. Since only add 4us dealy
	 in nxp_fspi_dll_calibration(), so do not distinguish different
	 platforms.
Patch 3: add max frequency limitation for different sample clock source
         selection. Datasheet give max 66MHz for mode 0 and 166MHz for
	 mode 3. And IC suggest to add this limitation on all SoCs for
	 safety and stability.