package/x11r7/xdriver_xf86-video-ati: don't override XDRIVER_XF86_VIDEO_ATI_CONF_OPTS

XDRIVER_XF86_VIDEO_ATI_CONF_OPTS is wrongly overridden in a conditional
since commit daa433bff6d2d9934705feacd3619a7618d13ae5

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/x11r7/xdriver_xf86-video-ati/xdriver_xf86-video-ati.mk

@@ -16,9 +16,9 @@ XDRIVER_XF86_VIDEO_ATI_DEPENDENCIES = \
 	xserver_xorg-server
 
 ifeq ($(BR2_PACKAGE_HAS_LIBEGL)$(BR2_PACKAGE_HAS_LIBGL)$(BR2_PACKAGE_LIBEPOXY),yyy)
-XDRIVER_XF86_VIDEO_ATI_CONF_OPTS = --enable-glamor
+XDRIVER_XF86_VIDEO_ATI_CONF_OPTS += --enable-glamor
 else
-XDRIVER_XF86_VIDEO_ATI_CONF_OPTS = --disable-glamor
+XDRIVER_XF86_VIDEO_ATI_CONF_OPTS += --disable-glamor
 endif
 
 # xdriver_xf86-video-ati requires O_CLOEXEC