usb: gadget: Check bmAttributes only if configuration is valid

If the USB configuration is not valid, then avoid checking for
bmAttributes to prevent null pointer deference.

Cc: stable <stable@kernel.org>
Fixes: 40e89ff5 ("usb: gadget: Set self-powered based on MaxPower and bmAttributes")
Signed-off-by: Prashanth K <prashanth.k@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250224085604.417327-1-prashanth.k@oss.qualcomm.com


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