lib/bch.c: use swap() to improve code

Use the swap() macro to simplify the functions solve_linear_system() and
gf_poly_gcd() and improve their readability.  Remove the local variable
tmp.

Fixes the following three Coccinelle/coccicheck warnings reported by
swap.cocci:

  WARNING opportunity for swap()
  WARNING opportunity for swap()
  WARNING opportunity for swap()

Link: https://lkml.kernel.org/r/20240708224023.9312-2-thorsten.blum@toblux.com
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: toblux

lib/bch.c

@@ -479,11 +479,8 @@ static int solve_linear_system(struct bch_control *bch, unsigned int *rows,
 		/* find suitable row for elimination */
 		for (r = p; r < m; r++) {
 			if (rows[r] & mask) {
-				if (r != p) {
-					tmp = rows[r];
-					rows[r] = rows[p];
-					rows[p] = tmp;
-				}
+				if (r != p)
+					swap(rows[r], rows[p]);
 				rem = r+1;
 				break;
 			}
@@ -799,21 +796,14 @@ static void gf_poly_div(struct bch_control *bch, struct gf_poly *a,
 static struct gf_poly *gf_poly_gcd(struct bch_control *bch, struct gf_poly *a,
 				   struct gf_poly *b)
 {
-	struct gf_poly *tmp;
-
 	dbg("gcd(%s,%s)=", gf_poly_str(a), gf_poly_str(b));
 
-	if (a->deg < b->deg) {
-		tmp = b;
-		b = a;
-		a = tmp;
-	}
+	if (a->deg < b->deg)
+		swap(a, b);
 
 	while (b->deg > 0) {
 		gf_poly_mod(bch, a, b, NULL);
-		tmp = b;
-		b = a;
-		a = tmp;
+		swap(a, b);
 	}
 
 	dbg("%s\n", gf_poly_str(a));