This commit renames USB PHY related HAL files from "usb_phy_xxx" to
"usb_fsls_phy_xxx" since they are only designed to support Full-Speed/Low-Speed
Serial USB PHYs. This renmaing is done to accommodate future USB PHYs that use
other PHY interfaces (e.g., UTMI, ULPI etc).
peripheral enable/disable usually should be managed by driver itself,
so make it as espressif private APIs, not recommended for user to use it
in application code.
However, if user want to re-write the driver or ports to other platform,
this is still possible by including the header in this way:
"esp_private/peripheral_ctrl.h"
