xprtrdma: Squelch kbuild sparse complaint

New complaint from kbuild for 4.9.y:

net/sunrpc/xprtrdma/verbs.c:489:19: sparse: incompatible types in
    comparison expression (different type sizes)

verbs.c:
489	max_sge = min(ia->ri_device->attrs.max_sge, RPCRDMA_MAX_SEND_SGES);

I can't reproduce this running sparse here. Likewise, "make W=1
net/sunrpc/xprtrdma/verbs.o" never indicated any issue.

A little poking suggests that because the range of its values is
small, gcc can make the actual width of RPCRDMA_MAX_SEND_SGES
smaller than the width of an unsigned integer.

Fixes: 16f906d ("xprtrdma: Reduce required number of send SGEs")
Signed-off-by: Chuck Lever <[email protected]>
Cc: [email protected]
Signed-off-by: Anna Schumaker <[email protected]>

net/sunrpc/xprtrdma/verbs.c

@@ -503,7 +503,8 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
 	struct ib_cq *sendcq, *recvcq;
 	int rc;
 
-	max_sge = min(ia->ri_device->attrs.max_sge, RPCRDMA_MAX_SEND_SGES);
+	max_sge = min_t(unsigned int, ia->ri_device->attrs.max_sge,
+			RPCRDMA_MAX_SEND_SGES);
 	if (max_sge < RPCRDMA_MIN_SEND_SGES) {
 		pr_warn("rpcrdma: HCA provides only %d send SGEs\n", max_sge);
 		return -ENOMEM;