mtd: nand: Add a NAND_CMD_STATUS when using write verification

To make sure the NAND chip is properly programmed we need a status
command before each page write. When CONFIG_MTD_NAND_VERIFY_WRITE=y this
assumption is broken when writing multiple pages consecutively. This
patch fixes this.

Signed-off-by: Bastian Hecht <hechtb@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>