Search in for KMS-capable drivers in extra/ as well

User can have an out-of-tree video driver supporting KMS installed;
Intel GMA500 drivers from RPM Fusion are one example of such module.

modules.d/50plymouth/installkernel

@@ -2,6 +2,6 @@
 # -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
 # ex: ts=8 sw=4 sts=4 et filetype=sh
 # Include KMS capable drm drivers
-for modname in $(find "$srcmods/kernel/drivers/gpu/drm" -name '*.ko' 2>/dev/null); do
+for modname in $(find "$srcmods/kernel/drivers/gpu/drm" "$srcmods/extra" -name '*.ko' 2>/dev/null); do
     grep -q drm_crtc_init  $modname && instmods $modname
 done