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

MFC after: 1 week
Sponsored by: Chelsio Communications