phy: da8xx-usb: rename clock con_ids

This renames the clock con_ids in the DA8XX USB PHY driver as well as
the matching names in the mach clock registration code.

This is in preparation for using device tree clocks where these names
will become part of the device tree bindings. The new names more closely
match the names used in the USB clock diagram in the SoC TRM.

Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>