The do_devinfo_subtree() function is only used if devinfo is compiled
in, so put it under the same ifdef. This avoids the following warning
when built with allnoconfig:
lib/driver.c:247: warning: 'do_devinfo_subtree' defined but not used
Signed-off-by: Robert Schwebel <r.schwebel@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>