drm/i915/display: Check mappable aperture when pinning preallocated vma

When system does not have mappable aperture, ggtt->mappable_end=0. In
this case if we pass PIN_MAPPABLE when pinning vma, the pinning code
will return -ENOSPC. So conditionally set PIN_MAPPABLE if HAS_GMCH().

Suggested-by: Chris P Wilson <chris.p.wilson@intel.com>
Signed-off-by: CQ Tang <cq.tang@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Ap Kamal <kamal.ap@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220315181425.576828-6-matthew.auld@intel.com