usb: dwc3: use devm_xxx functions

This patch enables to use devm_xxx functions during probing driver.
The devm_xxx series functions are able to release resource when the
driver is detatched. We can remove several codes to release resources
in the probe function.

Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>