drm/i915: Take pinning into account in __i915_gem_object_is_lmem

Don't blow up on a GEM_WARN_ON in __i915_gem_object_is_lmem if the
object is pinned (not evictable).

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210916162819.27848-6-matthew.brost@intel.com