mtd: nand: pxa3xx: Introduce 'marvell,armada370-nand' compatible string

This driver supports NFCv1 (as found in PXA SoC) and NFCv2 (as found in
Armada 370/XP SoC). As both controller has a few differences, a way of
distinguishing between the two is needed.

This commit introduces a new compatible string 'marvell,armada370-nand'
and assigns a compatible data of type enum pxa3xx_nand_variant to allow
such distinction.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Tested-by: Daniel Mack <zonque@gmail.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>