Revert "drm/i915: Preserve VGACNTR bits from the BIOS"

The VGA_2X_MODE bit apparently affects the display even when the VGA
plane is disabled. The bit will set by the BIOS when the panel width
is at least 1280 pixels. So by preserving the bit from the BIOS we
end up with corrupted display on machines with such high res panels.
I only have 1024x768 panels on my gen2 machines so never ran into
this problem.

The original reason for preserving the VGACNTR register was to make
my 830 survive S3 with acpi_sleep=s3_bios option. However after
further 830 fixes that option is no longer needed to make S3 work
and preserving VGACNTR doesn't seem to be necessary without it,
so we can just revert the entire patch.

This reverts
commit 69769f9a
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Fri Aug 15 01:22:08 2014 +0300

    drm/i915: Preserve VGACNTR bits from the BIOS

Cc: Bruno Prémont <bonbons@linux-vserver.org>
Cc: stable@vger.kernel.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=87171


Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>