Revert "package/libdrm: disable tests"

This reverts commit 3daacade133e40d38a38073c9ba9b1bf44c52c67.

The libdrm tests also include the useful command line utilities such as
modetest and modeprint, so leave them enabled.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libdrm/libdrm.mk

@@ -17,8 +17,7 @@ LIBDRM_DEPENDENCIES = \
 
 LIBDRM_CONF_OPTS = \
 	-Dcairo-tests=disabled \
-	-Dman-pages=disabled \
-	-Dtests=false
+	-Dman-pages=disabled
 
 ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
 LIBDRM_DEPENDENCIES += libatomic_ops