Revert "selftests/bpf: Update reg_bound range refinement logic"

This reverts commit da653de.
Removed logic is now covered by range_refine_in_halves()
which handles both 32-bit and 64-bit refinements.

Suggested-by: Paul Chaignon <paul.chaignon@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260306-bpf-32-bit-range-overflow-v3-3-f7f67e060a6b@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: eddyz87

tools/testing/selftests/bpf/prog_tests/reg_bounds.c

@@ -519,20 +519,6 @@ static struct range range_refine(enum num_t x_t, struct range x, enum num_t y_t,
 		return range_intersection(x_t, x, x_swap);
 	}
 
-	if (!t_is_32(x_t) && !t_is_32(y_t) && x_t != y_t) {
-		if (x_t == S64 && x.a > x.b) {
-			if (x.b < y.a && x.a <= y.b)
-				return range(x_t, x.a, y.b);
-			if (x.a > y.b && x.b >= y.a)
-				return range(x_t, y.a, x.b);
-		} else if (x_t == U64 && y.a > y.b) {
-			if (y.b < x.a && y.a <= x.b)
-				return range(x_t, y.a, x.b);
-			if (y.a > x.b && y.b >= x.a)
-				return range(x_t, x.a, y.b);
-		}
-	}
-
 	/* otherwise, plain range cast and intersection works */
 	return range_intersection(x_t, x, y_cast);
 }