Remove the event ring related checks in inc_enq()

Host hardware is the producer of events on the event ring,
driver will not queue anything, or call inc_enq() for the
event ring.
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>