pps gpio client: add missing dependency

Add "depends on GENERIC_HARDIRQS" to avoid compile breakage on s390:

drivers/built-in.o: In function `pps_gpio_remove':
linux-next/drivers/pps/clients/pps-gpio.c:189: undefined reference to `free_irq'
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: James Nuss <jamesnuss@nanometrics.ca>
Cc: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/pps/clients/Kconfig

@@ -31,7 +31,7 @@ config PPS_CLIENT_PARPORT
 
 config PPS_CLIENT_GPIO
 	tristate "PPS client using GPIO"
-	depends on PPS
+	depends on PPS && GENERIC_HARDIRQS
 	help
 	  If you say yes here you get support for a PPS source using
 	  GPIO. To be useful you must also register a platform device