i915: Fix obj size vs. alignment for drm_pci_alloc()

i915: Fix obj size vs. alignment for drm_pci_alloc()

drm_pci_alloc() refuses to cooperate if the passed alignment exceeds the
object size. So round up the obj size to the next power of two as well
to make this actually work.

Obviously things work just fine as long as the size was a power of two
to begin with. However kms_cursor_crc doesn't always use power of two
sizes so we hit a failure when we try to allocate the phys memory.

Testcase: igt/kms_cursor_crc
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170907143203.13055-1-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>