staging: drm/imx: add i.MX IPUv3 base driver

The IPU is the Image Processing Unit found on i.MX51/53/6 SoCs. It
features several units for image processing, this patch adds support
for the units needed for Framebuffer support, namely:

- Display Controller (dc)
- Display Interface (di)
- Display Multi Fifo Controller (dmfc)
- Display Processor (dp)
- Image DMA Controller (idmac)

This patch is based on the Freescale driver, but follows a different
approach. The Freescale code implements logical idmac channels and
the handling of the subunits is hidden in common idmac code pathes
in big switch/case statements. This patch instead just provides code
and resource management for the different subunits. The user, in this
case the framebuffer driver, decides how the different units play
together.

The IPU has other units missing in this patch:

- CMOS Sensor Interface (csi)
- Video Deinterlacer (vdi)
- Sensor Multi FIFO Controler (smfc)
- Image Converter (ic)
- Image Rotator (irt)

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>