usb: musb: core: Update the function description

Update the function description of musb_stage0_irq() to remove unused
parameter.

Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
[b-liu@ti.com: revised commit log]
Signed-off-by: Bin Liu <b-liu@ti.com>
Link: https://lore.kernel.org/r/20200115132547.364-2-b-liu@ti.com


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