wil6210: Never delete Rx chain with firmware

Firmware crash on attempt to delete Rx chain.
Driver part of Rx chain removed only in preparation for the target reset;
as reset is the only flow that removes Rx chain in the firmware.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>