eth: Rename and properly align br_reserved_address array

Since this array is no longer part of the bridge driver, it should
have an 'eth' prefix not 'br'.

We also assume that either it's 16-bit-aligned or the architecture has
efficient unaligned access.  Ensure the first of these is true by
explicitly aligning it.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>