net: libwx: improve flow control setting

net: libwx: improve flow control setting

Save the current mode of flow control, and enhance the statistics of
pause frames.

The received pause frames are divided into XON and XOFF to be counted.
And due to the hardware defect of SP devices, XON packets cannot be
trasmitted correctly, so Tx XON pause is disabled by default for those
devices.

Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Link: https://patch.msgid.link/20260407025616.33652-10-jiawenwu@trustnetic.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>