fix IS_I9XX macro in i915 DRM driver

Now that we're mapping registers in the DRM driver at load time, the
driver actually checks the PCI ID, so we need to make sure the macros
have all the right bits (and longer term use the DRM headers as the sole
copy of the PCI & register definitions).

This patch adds 945GME support to the DRM headers, fixing a regression
reported in http://bugzilla.kernel.org/show_bug.cgi?id=10395.

Tested-by: Alexander Oltu <alexander@all-2.com>
Signed-off-by: Jesse Barnes <jesse.barnes@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>