phy: stm32: add phy tuning support

It can be necessary to adjust the phys settings to compensate parasitics.
This patch adds support of new optional properties to configure the tune
interface of the phys of stm32-usbphyc.
Properties are optional, that's why each property is skipped if not
found (-EINVAL).
Phy tuning is restored on resume because if deep low power state is
achieved, phy tuning configuration is reset.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20211015161427.220784-4-amelie.delaunay@foss.st.com


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