drm/i915: Use might_alloc()

This maybe uses lockdep through the fs_reclaim annotations.

Signed-off-by: Bernard Zhao <bernard@vivo.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210429021327.57944-1-bernard@vivo.com