pch_gbe: fix error handling in pch_gbe_up()

If we fail to allocate rx buffers pool by any reason, we'll just return
with an error, however we've previously successfully requested an irq. Fix
this by releasing the irq before returning the error.

Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>