MIPS: AR7: use part_probe_types to specificy the partition parser to use

This patch changes the physmap-flash platform data on AR7 to pass the
correct partition parser: ar7part to used by the "physmap-flash" mapping
driver so we get the partitions probed correctly.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Cc: blogic@openwrt.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/4654/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>