drm/mgag200: Bug fix: Renesas board now selects native resolution.

drm/mgag200: Bug fix: Renesas board now selects native resolution.

Renesas boards were consistently defaulting to the 1024x768 resolution,
regardless of the native resolution of the monitor plugged in.  It was
determined that the EDID of the monitor was not being read.  Since the
DAC is a shared line, in order to read from or write to it we must take
control of the DAC clock.  This can be done by setting the proper
register to one.

This bug fix sets the register MGA1064_GEN_IO_CTL2 to one.  The DAC
control line can be used to determine whether or not a new monitor has
been plugged in.  But since the hotplug feature is not one we will
support, it has been decided to simply leave the register set to one.

Signed-off-by: Julia Lemire <jlemire@matrox.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>