gbm: Introduce modifiers into surface/bo creation

gbm: Introduce modifiers into surface/bo creation

The idea behind modifiers like this is that the user of GBM will have
some mechanism to query what properties the hardware supports for its BO
or surface. This information is directly passed in (and stored) so that
the DRI implementation can create an image with the appropriate
attributes.

A getter() will be added later so that the user GBM will be able to
query what modifier should be used.

Only in surface creation, the modifiers are stored until the BO is
actually allocated. In regular buffer allocation, the correct modifier
can (will be, in future patches be chosen at creation time.

v2: Make sure to check if count is non-zero in addition to testing if
calloc fails. (Daniel)

v3: Remove "usage" and "flags" from modifier creation. Requested by
Kristian.

v4: Take advantage of the "INVALID" modifier added by the GET_PLANE2
series.

v5: Don't bother with storing modifiers for gbm_bo_create because that's
a synchronous operation and we can actually select the correct modifier
at create time (done in a later patch) (Jason)

v6: Make modifier condition outside the check so that dri_use will work
properly (Jason)

Cc: Kristian Høgsberg <krh@bitplanet.net>
References (v4): https://lists.freedesktop.org/archives/intel-gfx/2017-January/116636.html
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com> (v1)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Acked-by: Daniel Stone <daniels@collabora.com>