egl/android: use drmDevice instead of the manual /dev/dri iteration

egl/android: use drmDevice instead of the manual /dev/dri iteration

Replace the manual handling of /dev/dri in favor of the drmDevice API.
The latter provides a consistent way of enumerating the devices,
providing device details as needed.

v2:
 - Use ARRAY_SIZE (Frank)
 - s/famour/favor/ typo (Frank)
 - Make MAX_DRM_DEVICES a macro - fix vla errors (RobF)
 - Remove left-over dev_path instance (RobF)

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Robert Foss <robert.foss@collabora.com> (v1)
Reviewed-by: Tomasz Figa <tfiga@chromium.org>