Use new std::simd fn in miri tests

Old fn were slightly divergent.

Author: workingjubilee

src/tools/miri/tests/pass/portable-simd-ptrs.rs

@@ -6,7 +6,7 @@ use std::simd::*;
 
 fn main() {
     // Pointer casts
-    let _val: Simd<*const u8, 4> = Simd::<*const i32, 4>::splat(ptr::null()).cast_ptr();
+    let _val: Simd<*const u8, 4> = Simd::<*const i32, 4>::splat(ptr::null()).cast();
     let addrs = Simd::<*const i32, 4>::splat(ptr::null()).expose_addr();
     let _ptrs = Simd::<*const i32, 4>::from_exposed_addr(addrs);
 }