mfd: remove ucb1400 support

The ucb1400 MFD driver and its gpio and touchscreen child
drivers were only used on a few PXA machines that were unused
for a while and are now removed.

Removing these leaves the AC97 support as ALSA specific,
no other drivers are now connected through this interface.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Lee Jones <lee@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Marek Vasut <marex@denx.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-gpio@vger.kernel.org
Cc: linux-input@vger.kernel.org
Cc: alsa-devel@alsa-project.org
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>