r8152: don't execute runtime suspend if the tx is not empty

r8152: don't execute runtime suspend if the tx is not empty

BugLink: http://bugs.launchpad.net/bugs/1662507
[ Upstream commit 6a0b76c04ec157c88ca943debf78a8ee58469f2d ]

Runtime suspend shouldn't be executed if the tx queue is not empty,
because the device is not idle.

Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>