mtd: mchp23k256: Add support for mchp23lcv1024

The mchp23lcv1024 is similar to the mchp23k256, the differences (from a
software point of view) are the capacity of the chip and the size of the
addresses used.

There is no way to detect the specific chip so we must be told via a
Device Tree or default to mchp23k256 when device tree is not used.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>