Fix for FBTFS in linaro/ubuntu

In file included from sunxi_mali_ump_dri2.c:39:0:
/usr/include/xf86drm.h:40:17: fatal error: drm.h: No such file or directory
compilation terminated.
make[2]: *** [sunxi_mali_ump_dri2.lo] Error 1

configure.ac

@@ -62,7 +62,7 @@ XORG_DRIVER_CHECK_EXT(RENDER, renderproto)
 XORG_DRIVER_CHECK_EXT(XV, videoproto)
 
 # Obtain compiler/linker options for the driver dependencies
-PKG_CHECK_MODULES(XORG, [xorg-server >= 1.0.99.901 xproto fontsproto $REQUIRED_MODULES])
+PKG_CHECK_MODULES(XORG, [xorg-server >= 1.0.99.901 xproto fontsproto xf86driproto libdrm $REQUIRED_MODULES])
 
 save_CFLAGS="$CFLAGS"
 CFLAGS="$XORG_CFLAGS"