usb: dwc3: core: add phy cleanup for probe error handling

Add the phy cleanup if dwc3 mode init fail, which is the missing part of
de-init for dwc3 core init.

Fixes: c499ff71 ("usb: dwc3: core: re-factor init and exit paths")
Cc: <stable@vger.kernel.org>
Signed-off-by: Li Jun <jun.li@nxp.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>