vrtc: change its year offset from 1960 to 1972

vrtc: change its year offset from 1960 to 1972

Real world year equals the value in vrtc YEAR register plus an offset.  We
used 1960 for original developepment as the offset to make leap year
consistent, but for a device's first use, its YEAR register is 0 and the
system year will be parsed as 1960 which is not a valid UNIX time and will
cause many applications to fail mysteriously.  Devices use 1972 instead to
fix this issue.

Updated patch which adds a sanity check suggested by Mathias

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>