usb: musb: tusb6010: uninitialized data in tusb_fifo_write_unaligned()

commit 517c7bf9 upstream.

This is writing to the first 1 - 3 bytes of "val" and then writing all
four bytes to musb_writel().  The last byte is always going to be
garbage.  Zero out the last bytes instead.

Fixes: 550a7375

 ("USB: Add MUSB and TUSB support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210916135737.GI25094@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>