i2c: mpc: Make use of i2c_recover_bus()

Move the existing calls of mpc_i2c_fixup() to a recovery function
registered via bus_recovery_info. This makes it more obvious that
recovery is supported and allows for a future where recovery is
triggered by the i2c core.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Wolfram Sang <wsa@kernel.org>