silence some warnings in hv.c

Since de0a224, xhv_keys and xhv_max
are the same type, so no casting needed

hv.c

@@ -817,7 +817,7 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 
 	xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
 	if (!counter) {				/* initial entry? */
-	} else if (xhv->xhv_keys > (IV)xhv->xhv_max) {
+	} else if (xhv->xhv_keys > xhv->xhv_max) {
 	    hsplit(hv);
 	} else if(!HvREHASH(hv)) {
 	    U32 n_links = 1;
@@ -2561,7 +2561,7 @@ S_share_hek_flags(pTHX_ const char *str, I32 len, register U32 hash, int flags)
 
 	xhv->xhv_keys++; /* HvTOTALKEYS(hv)++ */
 	if (!next) {			/* initial entry? */
-	} else if (xhv->xhv_keys > (IV)xhv->xhv_max /* HvKEYS(hv) > HvMAX(hv) */) {
+	} else if (xhv->xhv_keys > xhv->xhv_max /* HvKEYS(hv) > HvMAX(hv) */) {
 		hsplit(PL_strtab);
 	}
     }