usb: isp1760: do not reset retval

We do not really need to reset retval before get used bellow.
This will avoid the clang-analyzer warning:

drivers/usb/isp1760/isp1760-hcd.c:1919:2: warning: Value stored to 'retval' is never read [clang-analyzer-deadcode.DeadStores]
        retval = 0;

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Link: https://lore.kernel.org/r/20210819180929.1327349-4-rui.silva@linaro.org


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