ARM: 6366/1: Update U300 defconfig

This mainly removes a lot of unused subsystems (as for the mainline
drivers) in the U300 defconfig, switch of MMC debugging by default
and enables debugfs on the builds. Once we merge the drivers we'll
configure it on again.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>