fou: Don't use const __read_mostly

const __read_mostly is a senseless combination. If something
is already const it cannot be __read_mostly. Remove the bogus
__read_mostly in the fou driver.

This fixes section conflicts with LTO.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>