drivers/rtc/rtc-ds1307.c: add support for RTC device pt7c4338

PT7C4338 chip is being manufactured by Pericom Technology Inc. It is a
serial real-time clock which provides:

1) Low-power clock/calendar.
2) Programmable square-wave output.

It has 56 bytes of nonvolatile RAM. Its register set is same as that of
rtc device: DS1307.

Signed-off-by: Priyanka Jain <[e-mail]>
Acked-by: Timur Tabi <[e-mail]>
Reviewed-by: Wolfram Sang <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-ds1307.c

···
 	{ "ds1340", ds_1340 },
 	{ "ds3231", ds_3231 },
 	{ "m41t00", m41t00 },
+	{ "pt7c4338", ds_1307 },
 	{ "rx8025", rx_8025 },
 	{ }
 };