drm/i915: Use the GM45 VGA hotplug workaround on G45 as well.

Although spec say CRT_HOTPLUG_ACTIVATION_PERIOD_64 is only useful for
mobile platform, it is also required to detect vga on G4x desktops correctly.
Tested on G45/G43/Q45 platforms with no regressions.

It fixed freedesktop.org bug #21120 and part of bug #21210

Signed-off-by: Ma Ling <[e-mail]>
Signed-off-by: Eric Anholt <[e-mail]>

drivers/gpu/drm/i915/intel_crt.c

···
 	hotplug_en &= CRT_FORCE_HOTPLUG_MASK;
 	hotplug_en |= CRT_HOTPLUG_FORCE_DETECT;
 
-	if (IS_GM45(dev))
+	if (IS_G4X(dev))
 		hotplug_en |= CRT_HOTPLUG_ACTIVATION_PERIOD_64;
 
 	hotplug_en |= CRT_HOTPLUG_VOLTAGE_COMPARE_50;