mtd: nand: ams-delta: select for built-in by default

Now that the Amstrad Delta NAND driver is converted to a platform driver,
which prevents it from interfering with other unrelated hardware in multiple
OMAP1 cpu and machine configurations, it can be automatically configured for
being built into the kernel if the Amstrad Delta board is also selected.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>