Octeontx2-af: Fix an issue in firmware shared data reserved space

The last patch which added support to extend the firmware shared
data to add channel data information has introduced a bug due to
the reserved space not adjusted accordingly.

This patch fixes the issue and also adds BUILD_BUG to avoid this
regression error.

Fixes: 99781449 ("Octeontx2-af: Fetch MAC channel info from firmware")
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>