usb: dwc3: Fix a repeated word checkpatch warning

Fixes a repeated word checkpatch warning in ep0.c by removing the repeated
'only' word.

Signed-off-by: Kushagra Verma <kushagra765@outlook.com>
Link: https://lore.kernel.org/r/HK0PR01MB2801996E815208393170010FF8D39@HK0PR01MB2801.apcprd01.prod.exchangelabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>