uboot-imx

MLK-14938-19 spi: Add FlexSPI Driver for i.MX8QM

Add fsl_fspi driver for flexspi controller. This driver supports:
1. DDR Quad output
2. Prefetch function for improve read performance.
3. Fast read and Quad read for one line read mode.
4. Read flash FSR register.
5. DM.

Signed-off-by: Han Xu <han.xu@nxp.com>
Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit ae4e80b7b0debd2ad868781aaeb28ca4f2d9a8aa)
(cherry picked from commit dcd5504f6493d9aed415f397f1c13611fc202605)