phy: Add new phy_notify_state() api

Peter Griffin <peter.griffin@linaro.org> says:

This series adds a new phy_notify_state() API to the phy subsystem. It is
designed to be used when some specific runtime configuration parameters
need to be changed when transitioning to the desired state which can't be
handled by phy_calibrate()or phy_power_{on|off}().

The first user of the new API is phy-samsung-ufs and phy-gs101-ufs which
need to issue some register writes when entering and exiting the hibern8
link state.

A separate patch will be sent for ufs-exynos driver to make use of this new
API in the hibern8 callbacks.

Link: https://patch.msgid.link/20251112-phy-notify-pmstate-v5-0-39df622d8fcb@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>