mtd: mxc_nand: add RESET command support

mxc_nand driver must support the RESET Command in order to support
Micron NAND which need a reset before any other command.

Signed-off-by: Eric Benard <eric@eukrea.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>