i2c: mv64xxx: Remove shutdown method from driver

When I attempt to shut down (or reboot) my R8 based NTC CHIP with this
i2c driver I get the following error: "i2c i2c-0: mv64xxx: I2C bus
locked, block: 1, time_left: 0". Reboots are successful but shutdowns
freeze. If I comment out the shutdown routine the device both reboots
and shuts down successfully without receiving this error (however it
does receive a warning of missing atomic_xfer).

It appears that very few i2c drivers have a shutdown method, I assume
because these devices are often used to communicate with PMICs (such
as in my case with the R8 based NTC CHIP). I'm proposing we simply
remove this method so long as it doesn't cause trouble for others
downstream. I'll work on an atomic_xfer method and submit that in
a different patch.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Acked-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>