staging: et131x: Remove dead code in isr

Dan Carpenter reports:
The patch c2ebf58b: "staging: et131x: Implement NAPI support"
from Aug 21, 2014, leads to the following static checker warning:

        drivers/staging/et131x/et131x.c:4004 et131x_isr()
        warn: we tested 'status' before and it was 'true'

We don't actually need the dead code, as we're now using NAPI to
handle enabling interrupts - but we do need to enable interrupts if
NAPI is not scheduled - so enable interrupts if this is the case.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>