mtd: nand: pxa3xx: use marvell, prefix for custom DT properties

mtd: nand: pxa3xx: use marvell, prefix for custom DT properties

The DT properties for the "enable-arbiter" and "keep-config" config
knobs were previously named inconsistently:

- The u-boot driver used "nand-enable-arbiter" and "nand-keep-config"
  names, without Marvell prefixes.

- The Linux driver uses "marvell,nand-keep-config" ("enable-arbiter"
  does not exist anymore in recent kernels, but it also used to be
  "marvell,nand-enable-arbiter").

- The device trees almost all use "marvell," prefixed names, except for
  one single instance of "nand-enable-arbiter" without vendor prefix.

This commit standardizes on the vendor prefixed version, making the
u-boot driver read from DT props "marvell,nand-enable-arbiter" and
"marvell,nand-keep-config". The one device tree using the unprefixed
version is also changed to use the new naming.

This has the side effect of making the previously no-op "marvell,"
config knobs already present in some DTs actually do something. This was
likely the original intention of the DT authors, but note that this
commit was not tested on every single impacted board.

Signed-off-by: Pierre Bourdon <delroth@gmail.com>