libdrm: change .bbappend to use %

Change file name to use % and append against any revision of the main
libdrm recipe.   This makes updating the .bbappend file name only
necessary if recipe itself needs to change.

Signed-off-by: John Weber <rjohnweber@gmail.com>

diff --git a/meta-fsl-arm/recipes-graphics/drm/libdrm_2.4.49.bbappend b/meta-fsl-arm/recipes-graphics/drm/libdrm_%.bbappend
similarity index 100%
rename from meta-fsl-arm/recipes-graphics/drm/libdrm_2.4.49.bbappend
rename to meta-fsl-arm/recipes-graphics/drm/libdrm_%.bbappend