OMAP1: Amstrad Delta: modify defconfig for external keyboardsupport

The patch adds a CONFIG directive required for supporting the Amstrad Delta
connected external keyboard by default.

Created and tested against linux-omap master,
commit 104a77440f05430f29f9d3f4ecb88c1536819585 dated 2010-04-27.

Works on top of PATCH v4 4/5(7), "input: serio: add support for Amstrad Delta
serial keyboard port".

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: Tony Lindgren <tony@atomide.com>