udev: directly import the device groups

No need for the indirection of PROGRAM, then ENV for the output value.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

udev/80-libinput-device-groups.rules.in

 ACTION!="add|change", GOTO="libinput_device_group_end"
 KERNEL!="event[0-9]*", GOTO="libinput_device_group_end"
 
-ATTRS{phys}=="?*", \
-	ENV{LIBINPUT_DEVICE_GROUP}=="", \
-	PROGRAM="@UDEV_TEST_PATH@libinput-device-group %S%p", \
-	ENV{LIBINPUT_DEVICE_GROUP}="%c"
+ATTRS{phys}=="?*", IMPORT{program}+="@UDEV_TEST_PATH@libinput-device-group %S%p"
 
 LABEL="libinput_device_group_end"

udev/libinput-device-group.c

@@ -247,7 +247,7 @@ int main(int argc, char **argv)
 	if (str && str > strrchr(group, '-'))
 		*str = '\0';
 
-	printf("%s\n", group);
+	printf("LIBINPUT_DEVICE_GROUP=%s\n", group);
 
 	rc = 0;
 out: