phy: stm32: don't print an error on probe deferral

Change stm32-usbphyc driver to not print an error message when the device
probe operation is deferred.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Link: https://lore.kernel.org/r/20201110130531.7610-1-amelie.delaunay@st.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>