[ARM] pxa: add basic support for the Aeronix Zipit Z2 handheld

This patch adds support for the Zipit Z2. The parts missing from this
patch are the battery support, SPI driver for the LCD and support for
the Silicon Serial ID chip.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>