package/mesa3d: fix build with egl but without drm, wayland or x11

package/mesa3d: fix build with egl but without drm, wayland or x11

A user can enable mesa3d and EGL by selecting
BR2_PACKAGE_MESA3D_OPENGL_EGL

This will result in a build failure if the user does not select a driver
that enables drm, wayland or x11 as platforms will be empty.

To fix this build failure, always enable surfaceless platform which
defining property is that it has no native surfaces:
https://gitlab.freedesktop.org/mesa/mesa/blob/master/docs/specs/EGL_MESA_platform_surfaceless.txt

Fixes:
 - http://autobuild.buildroot.org/results/8960b950f79be82f81db20be41fa4b47bc76dee8

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