lib: hash: follow-up fixups for arch hash

This patch adds the include file to pull in __read_mostly on some
architectures e.g. ppc and also fixes up signatures in generic
asm.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Francesco Fusco <ffusco@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/asm-generic/hash.h
Simple merge

diff --cc lib/hash.c
Simple merge