drm/i915: Resolving the memory region conflict for Stolen area

There is a conflict seen when requesting the kernel to reserve
the physical space used for the stolen area. This is because
some BIOS are wrapping the stolen area in the root PCI bus, but have
an off-by-one error. As a workaround we retry the reservation with an
offset of 1 instead of 0.

v2: updated commit message & the comment in source file (Daniel)

Signed-off-by: Akash Goel <akash.goel@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>