spi: pxa2xx: Balance runtime PM enable/disable on error

Don't undo the PM initialization if we error out before we managed to
initialize it. The call to pm_runtime_disable() without being preceded
by pm_runtime_enable() would disturb the balance of the Force.

In practice, this happens if we fail to allocate any of the GPIOS ("cs",
"ready") due to -EPROBE_DEFER because we're getting probled before the
GPIO driver.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Link: https://lore.kernel.org/r/20190719122713.3444318-1-lkundrak@v3.sk
Signed-off-by: Mark Brown <broonie@kernel.org>