Add simd_masked_{load,store} platform-intrinsics

This maps to the LLVM intrinsics: llvm.masked.load and llvm.masked.store

compiler/rustc_span/src/symbol.rs

@@ -1516,6 +1516,8 @@ symbols! {
         simd_insert,
         simd_le,
         simd_lt,
+        simd_masked_load,
+        simd_masked_store,
         simd_mul,
         simd_ne,
         simd_neg,