driver core: Annotate dev_err_probe() with __must_check

We have got already new users of this API which interpret it differently
and miss the opportunity to optimize their code.

In order to avoid similar cases in the future, annotate dev_err_probe()
with __must_check.

Fixes: a787e540

 ("driver core: add device probe log helper")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200826104459.81979-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>