This patch adds support for the ST M41T00 I2C RTC chip.

This rtc chip has no mechanism to freeze it's registers while being
read; however, it will delay updating the external values of the
registers for 250ms after a register is read.  To ensure that a sane
time value is read, the driver verifies that the same registers values
were read twice before returning.

Also, when setting the rtc from an interrupt handler, a tasklet is used
to provide the context required by the i2c core code.
Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>