MFC r339700:

cxgbe(4): new sysctl to display the start of the RSS region for a VI.

dev.<ifname>.<inst>.rss_base

For example:
dev.cc.0.rss_base: 0
dev.cc.1.rss_base: 128
dev.vcc.0.rss_base: 256
dev.vcc.1.rss_base: 384

Sponsored by: Chelsio Communications