xdiff: drop xpparam_t parameter from histogram cmp_recs()

Since 663c5ad035 (diff histogram: intern strings, 2021-11-17), our
cmp_recs() does not call xdl_recmatch(), and thus no longer needs an
xpparam_t struct from which to get the flags. We can drop the unused
parameter from the function, as well as the macro which wraps it.

There's no functional change here; it's just simplifying things (and
making -Wunused-parameter happier).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

xdiff/xhistogram.c

@@ -88,15 +88,14 @@ struct region {
 #define REC(env, s, l) \
 	(env->xdf##s.recs[l - 1])
 
-static int cmp_recs(xpparam_t const *xpp,
-	xrecord_t *r1, xrecord_t *r2)
+static int cmp_recs(xrecord_t *r1, xrecord_t *r2)
 {
 	return r1->ha == r2->ha;
 
 }
 
 #define CMP(i, s1, l1, s2, l2) \
-	(cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
+	(cmp_recs(REC(i->env, s1, l1), REC(i->env, s2, l2)))
 
 #define TABLE_HASH(index, side, line) \
 	XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)