adding pxa3xx_nand_flash to platform data

[Siddarth Gore]

Hello Eric,

Currently I need to enable the deprecated MTD_NAND_PXA3xx_BUILTIN
support for Aspenite DB board (pxa168). I have a patch ready to add
pxa3xx_nand_flash in aspenite.c but I was wondering about the cmdset
field in it.
Looks like it is the same for all boards (depending upon the page size).
So should I add it to the board specific setup file or remove it from
pxa3xx_nand_platform_data (and put it in say, pxa3xx_nand_info)?

If there are boards which require a different cmdset then we have to go
with first option, if not, we can use option two and save some code
duplication.

-siddarth