phy: stm32: rework PLL Lock detection

phy: stm32: rework PLL Lock detection

USBPHYC has a register per phy to control and monitor the debug interface
of the HS PHY through a digital debug access.
With this register, it is possible to know if PLL Lock input to phy is
high. That means the PLL is ready for HS operation.
Instead of using an hard-coded delay after PLL enable and PLL disable, use
this bit to ensure good operating of the HS PHY.
Also use an atomic counter (n_pll_cons) to count the actual number of PLL
consumers and get rid of stm32_usbphyc_has_one_phy_active.
The boolean active in the usbphyc_phy structure is kept, because we need to
know in remove if a phy_exit is required to properly disable the PLL.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20210105090525.23164-7-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>