travis: correct libdrm required regex to also track libdrm itself

The current regex was tracking only the libdrm_foo packages, while with
recent changed we bumped only (and rightfully so) libdrm.

Fix the regex to track any libdrm package.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Rhys Kidd <rhyskidd@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
diff --git a/.travis.yml b/.travis.yml
index dfbc052..e8426e9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -47,7 +47,7 @@
 
   # Since libdrm gets updated in configure.ac regularly, try to pick up the
   # latest version from there.
-  - for line in `grep "^LIBDRM_.*_REQUIRED=" configure.ac`; do
+  - for line in `grep "^LIBDRM.*_REQUIRED=" configure.ac`; do
       old_ver=`echo $LIBDRM_VERSION | sed 's/libdrm-//'`;
       new_ver=`echo $line | sed 's/.*REQUIRED=//'`;
       if `echo "$old_ver,$new_ver" | tr ',' '\n' | sort -Vc 2> /dev/null`; then