firmware: microchip: auto-update: fix poll_complete() to not report spurious timeout...

firmware: microchip: auto-update: fix poll_complete() to not report spurious timeout errors

fw_upload's poll_complete() is really intended for use with
asynchronous write() implementations - or at least those where the
write() loop may terminate without the kernel yet being aware of whether
or not the firmware upload has succeeded. For auto-update, write() is
only ever called once and will only return when uploading has completed,
be that by passing or failing. The core fw_upload code only calls
poll_complete() after the final call to write() has returned.

However, the poll_complete() implementation in the auto-update driver
was written to expect poll_complete() to be called from another context,
and it waits for a completion signalled from write(). Since
poll_complete() is actually called from the same context, after the
write() loop has terminated, wait_for_completion() never sees the
completion get signalled and always times out, causing programming to
always report a failing.

Since write() is full synchronous, and its return value will indicate
whether or not programming passed or failed, poll_complete() serves no
purpose and can be cut down to simply return FW_UPLOAD_ERR_NONE.

Cc: stable@vger.kernel.org
Fixes: ec5b0f1193ad4 ("firmware: microchip: add PolarFire SoC Auto Update support")
Reported-by: Jamie Gibbons <jamie.gibbons@microchip.com>
Tested-by: Jamie Gibbons <jamie.gibbons@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>