Add Bus class to reset OCC bus driver

For some systems, the OCC is accessed over the SBEFIFO, acting as a bus.
If the SBE experiences a failure, the SBEFIFO driver is unable to
recover. Therefore, the OCC control application  must force a reset of
the SBEFIFO driver when the OCC goes active.

Add a Bus class and reset method to unbind and bind the appropriate
SBEFIFO devices when the OCC devices are bound.

Testing: Powered on the system successfully. Injected SBE error through
a putscom. Without this fix, I intermittently saw SBEFIFO errors on the
BMC after the injection. With the fix, I saw no errors despite ~20
iterations.

Resolves openbmc/openbmc#3156

Change-Id: I0f9a230c57d0a3a7b59a874f62cdb1d93c6dcdfb
Signed-off-by: Eddie James <eajames@us.ibm.com>
6 files changed