egl: automake: remove unused HAVE_XCB_DRI2 define

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/egl/main/Makefile.am

@@ -68,7 +68,6 @@ endif
 
 if HAVE_EGL_DRIVER_DRI2
 AM_CFLAGS += -D_EGL_BUILT_IN_DRIVER_DRI2
-AM_CFLAGS += -DHAVE_XCB_DRI2
 libEGL_la_LIBADD += ../drivers/dri2/libegl_dri2.la
 libEGL_la_LIBADD += $(DLOPEN_LIBS) $(LIBDRM_LIBS)
 endif