drivers/video: fsl-diu-fb: fix some ioctls

Use the _IOx macros to define the ioctl commands, instead of hard-coded
numbers.  Unfortunately, the original definitions of MFB_SET_PIXFMT and
MFB_GET_PIXFMT used the wrong value for the size, so these macros have
new values now.  To avoid breaking binary compatibility with older
applications, we retain support for the original values, but the driver
displays a warning message if they're used.

Also remove the FBIOGET_GWINFO and FBIOPUT_GWINFO ioctls.  FBIOPUT_GWINFO
was never implemented, and FBIOGET_GWINFO was never used by any
application.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>