uboot-phytec

kw_spi: backup and reset the MPP of the chosen CS pin

This was not done before, and in the case of a shared pin (for MPP0
between NF_IO[2] and CSn) this could lead to problems.

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Holger Brunck <holger.brunck@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>