spi: stm32: fix pm_runtime_get_sync() error checking

The pm_runtime_get_sync() can return either 0 or 1 on success but this
code treats 1 as a failure.

Fixes: db96bf97 ("spi: stm32: fixes suspend/resume management")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Alain Volmat <alain.volmat@st.com>
Link: https://lore.kernel.org/r/20200909094304.GA420136@mwanda


Signed-off-by: Mark Brown <broonie@kernel.org>