net/e1000: fix i219 hang on reset/close

net/e1000: fix i219 hang on reset/close

Unit hang may occur if multiple descriptors are available in the rings
during reset or close. This state can be detected by configure status
by bit 8 in register. If the bit is set and there are pending
descriptors in one of the rings, we must flush them before reset or
close.

Fixes: 805803445a02 ("e1000: support EM devices (also known as e1000/e1000e)")
Cc: stable@dpdk.org
Signed-off-by: Xiao Zhang <xiao.zhang@intel.com>
Reviewed-by: Xiaolong Ye <xiaolong.ye@intel.com>