package/mpv: vaapi-drm needs egl-drm

package/mpv: vaapi-drm needs egl-drm

Build of vaapi-drm without egl-drm is broken since commit
6ec47c4e59c7c8c57e972dab985c8a2ba0bf7174.

egl-drm has been added with commit
031df474c24f92757ac95ade572b90995ebdc6a2 and it is only available with
mesa3d because of the gbm dependency:
https://github.com/mpv-player/mpv/blob/0b56e1c00a57fdb767674462c299a5c973a9e373/wscript#L571

Indeed, at the moment, mesa3d is the only gbm provider in buildroot.

Fixes:
 - http://autobuild.buildroot.org/results/83d6dcbb77ab8754aefcdcf90baeaff9db2a1c81

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>