Reduce the priority of cxgbei(4) driver, so it doesn't get chosen
by default. This is a workaround for a too simplistic ICL module
choosing mechanism. To use it, specify offload in ctl.conf
or iscsi.conf.

This fixes a problem where "kldload cxgbei" wedges the iSCSI stack,
if you don't have a Chelsio card installed, or the endpoints of the
iSCSI session are not reachable through addresses configured
on that interface.

Reviewed by: np@
MFC after: 1 month