spi: pic32-sqi: fixup wait_for_completion_timeout return handling

wait_for_completion_timeout returns unsigned long not int so the check for
<= 0 should be == 0 here, and the type unsigned long. The function return
is set to -ETIMEDOUT to reflect the actual problem.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>