egl: implement eglQueryDmaBufModifiersEXT

egl: implement eglQueryDmaBufModifiersEXT

query and return supported dmabuf format modifiers for
EGL_EXT_image_dma_buf_import_modifiers.

v2: move format check to the driver instead of making format queries
   here and then checking.
v3: Check DRIimageExtension version before query (Daniel Stone)
v4:
- move to DRIimageExtension version 15, check queryDmaBufModifiers before
  calling (Jason Ekstrand)
- pass external_only to the driver instead of setting as EGL_TRUE here
  (Emil Velikov, Daniel Stone)

Signed-off-by: Varad Gautam <varad.gautam@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>