[MTD] [NAND] pxa3xx_nand: allow to disable builtin flash-type table

This patch adds a MTD_NAND_PXA3xx_BUILTIN configuration variables which
allows to disable usage of builtin flash-type table.  Not enabling this
option saves some space in the generated driver.

Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>