usb: gadget: f_tcm: Fix Get/SetInterface return value

usb: gadget: f_tcm: Fix Get/SetInterface return value

Check to make sure that the GetInterface and SetInterface are for valid
interface. Return proper alternate setting number on GetInterface.

Fixes: 0b8b1a1fede0 ("usb: gadget: f_tcm: Provide support to get alternate setting in tcm function")
Cc: stable@vger.kernel.org
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/ffd91b4640945ea4d3b4f4091cf1abbdbd9cf4fc.1733876548.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>