ptp: Added a brand new class driver for ptp clocks.

This patch adds an infrastructure for hardware clocks that implement
IEEE 1588, the Precision Time Protocol (PTP). A class driver offers a
registration method to particular hardware clock drivers. Each clock is
presented as a standard POSIX clock.

The ancillary clock features are exposed in two different ways, via
the sysfs and by a character device.

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index 75cf611..4585836 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -302,6 +302,7 @@
 header-y += ppp_defs.h
 header-y += pps.h
 header-y += prctl.h
+header-y += ptp_clock.h
 header-y += ptrace.h
 header-y += qnx4_fs.h
 header-y += qnxtypes.h