nand: mxs: fix error handling for mxs_nand_init

nand: mxs: fix error handling for mxs_nand_init

Fix error handling for mxs_nand_init.

The original error handling is wrong for err2 and err1.
Should first free desc[x], then free desc.

This patch also correctly handle err3, should use
MXS_DMA_CHANNEL_AHB_APBH_GPMI0 as the check point.

Cc: Stefano Babic <[email protected]>
CC: Fabio Estevam <[email protected]>
Cc: Scott Wood <[email protected]>
Cc: Marek Vasut <[email protected]>
Signed-off-by: Peng Fan <[email protected]>
Reviewed-by: Marek Vasut <[email protected]>