fsi: sbefifo: Add sysfs file indicating a timeout error

The SBEFIFO timeout error requires special handling in userspace
to do recovery operations. Add a sysfs file to indicate a timeout
error, and notify pollers when a timeout occurs.

This will be used by the openpower-occ-control application.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20211019211749.38059-3-eajames@linux.ibm.com


Signed-off-by: Joel Stanley <joel@jms.id.au>