FROMLIST: fb: add dma-buf support

FROMLIST: fb: add dma-buf support

Add support for the dma-buf exporter role to the frame buffer API. The
importer role isn't meaningful for frame buffer devices, as the frame
buffer device model doesn't allow using externally allocated memory.

taken from an RFC on the linaro-mm-sig mailing list:
http://lists.linaro.org/pipermail/linaro-mm-sig/2012-June/002167.html

Fixes by Mark Yao:
  add FBIOGET_DMABUF to compat_ioctl.

Change-Id: I39c9bbdd6b88c6d5ba7524abfc5b560dceb4633e
Signed-off-by: Guillaume Tucker <guillaume.tucker@arm.com>
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
(am from https://patchwork.linuxtv.org/patch/12980)