Merge commit '90ba25b7' of...

Merge commit '90ba25b7' of https://source.denx.de/u-boot/custodians/u-boot-nand-flash

In preparation of re-sync of mtd stack, we opt to move the current stack
slowly in order to have a more easy sync and test. We would like to
prepare uboot to support no-jedec and no-onfi compliant nand so we need
to clean up a bit the code we have now and upstream some of the support.
In this series we expect no functional change

Tested on:
 - imx6ull Micron   MT29F2G08ABAGAH4
 - imx8mn  Macronix MX30LF4G18AC