lib: Add missing arch generic-y entries for asm-generic/hash.h

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/ia64/include/asm/Kbuild

@@ -4,4 +4,5 @@ generic-y += exec.h
 generic-y += kvm_para.h
 generic-y += trace_clock.h
 generic-y += preempt.h
-generic-y += vtime.h
+generic-y += vtime.h
+generic-y += hash.h