usb: dwc3: gadget: Remove redundant assignment to pointer trb

usb: dwc3: gadget: Remove redundant assignment to pointer trb

The pointer trb is being assigned a value that is not being
read afterwards, it is being re-assigned later inside a for_each_sg
loop. The assignment is redundant and can be removed.

Cleans up clang scan warning:
drivers/usb/dwc3/gadget.c:3432:19: warning: Value stored to 'trb'
during its initialization is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20240207120319.2445123-1-colin.i.king@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>