Add reference to CAPI 2.0 standard

Move the entry about CAPI 2.0 to the beginning and add a URL.
Incorporate changes suggested by Randy Dunlap, thanks for proofreading.

Signed-off-by: Karsten Keil <keil@b1-systems.de>
Signed-off-by: David S. Miller <davem@davemloft.net>