pps: add kernel consumer support

Add an optional feature of PPSAPI, kernel consumer support, which uses the
added hardpps() function.

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/ioctl/ioctl-number.txt

@@ -247,7 +247,7 @@ Code  Seq#(hex)	Include File		Comments
 'p'	40-7F	linux/nvram.h
 'p'	80-9F	linux/ppdev.h		user-space parport
 					<mailto:tim@cyberelk.net>
-'p'	A1-A4	linux/pps.h		LinuxPPS
+'p'	A1-A5	linux/pps.h		LinuxPPS
 					<mailto:giometti@linux.it>
 'q'	00-1F	linux/serio.h
 'q'	80-FF	linux/telephony.h	Internet PhoneJACK, Internet LineJACK