myri10ge: Rename DCA-related firmware counters

Rename the cryptic "dca_capable" to "dca_capable_firmware"
and "dca_enabled" to "dca_device_present" in the firmware
counters.

Signed-off-by: Brice Goglin <brice@myri.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>