drivers/w1/slaves/w1_ds2408.c: add magic sequence to disable P0 test mode

drivers/w1/slaves/w1_ds2408.c: add magic sequence to disable P0 test mode

Power-up timing

The DS2408 is sensitive to the power-on slew rate and can inadvertently
power up with a test mode feature enabled.  When this occurs, the P0 port
does not respond to the Channel Access Write command.  For most reliable
operation, it is recommended to disable the test mode after every power-on
reset using the Disable Test Mode sequence shown below.  The 64-bit ROM
code must be transmitted in the same bit sequence as with the Match ROM
command, i.e., least significant bit first.  This precaution is
recommended in parasite power mode (VCC pin connected to GND) as well as
with VCC power.

Disable Test Mode:
RST,PD,96h,<64-bit DS2408 ROM Code>,3Ch,RST,PD

Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>