sfc: Update hardware definitions for Siena

Siena is still based on the Falcon hardware architecture and will
share many of these definitions, so replace falcon_hwdefs.h with
regs.h.

The new definitions have been generated according to a naming
convention which incorporates the type and revision information.
Update the code accordingly.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>