fsi: scom: Fix error handling

SCOM error handling is made complex by trying to pass around two bits of
information: the function return code, and a status parameter that
represents the CFAM error status register.

The commit f72ddbe1d7b7 ("fsi: scom: Remove retries") removed the
"hidden" retries in the SCOM driver, in preference of allowing the
calling code (userspace or driver) to decide how to handle a failed
SCOM. However it introduced a bug by attempting to be smart about the
return codes that were "errors" and which were ok to fall through to the
status register parsing.

We get the following errors:

 - EINVAL or ENXIO, for indirect scoms where the value is invalid
 - EINVAL, where the size or address is incorrect
 - EIO or ETIMEOUT, where FSI write failed (aspeed master)
 - EAGAIN, where the master detected a crc error (GPIO master only)
 - EBUSY, where the bus is disabled (GPIO master in external mode)

In all of these cases we should fail the SCOM read/write and return the
error.

Thanks to Dan Carpenter for the detailed bug report.

Fixes: f72ddbe1d7b7 ("fsi: scom: Remove retries")
Link: https://lists.ozlabs.org/pipermail/linux-fsi/2021-November/000235.html
Reported-by: Dan Carpenter <[email protected]>
Signed-off-by: Joel Stanley <[email protected]>
Reviewed-by: Eddie James <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joel Stanley <[email protected]>

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