cxgbe(4): Make sure suspend/resume works in recovery mode.

The driver does minimal initialization in this mode and suspend/resume
should ignore resources that aren't setup. This is for debug only.

kenv hw.cxgbe.sos="1"
kldload if_cxgbe
devctl suspend t6nex0
devctl resume t6nex0

Sponsored by: Chelsio Communications

(cherry picked from commit f4ab14044c1de35b1aefad5449bddc5a1272f8d9)