llvm: switch most targets to using half and fp128 IR types

As of LLVM 22, most backends can (finally) handle legalization of these types as
necessary, so we don't need to do it ourselves anymore.

closes https://github.com/ziglang/zig/issues/23674

src/codegen/llvm.zig

@@ -4646,20 +4646,6 @@ fn toLlvmGlobalAddressSpace(wanted_address_space: std.builtin.AddressSpace, targ
 /// or if it produces miscompilations.
 pub fn backendSupportsF16(target: *const std.Target) bool {
     return switch (target.cpu.arch) {
-        // https://github.com/llvm/llvm-project/issues/97981
-        .csky,
-        // https://github.com/llvm/llvm-project/issues/97981
-        .powerpc,
-        .powerpcle,
-        .powerpc64,
-        .powerpc64le,
-        // https://github.com/llvm/llvm-project/issues/97981
-        .wasm32,
-        .wasm64,
-        // https://github.com/llvm/llvm-project/issues/97981
-        .sparc,
-        .sparc64,
-        => false,
         .arm,
         .armeb,
         .thumb,
@@ -4686,11 +4672,6 @@ pub fn backendSupportsF128(target: *const std.Target) bool {
     return switch (target.cpu.arch) {
         // https://github.com/llvm/llvm-project/issues/121122
         .amdgcn,
-        // Test failures all over the place.
-        .mips64,
-        .mips64el,
-        // https://github.com/llvm/llvm-project/issues/41838
-        .sparc,
         => false,
         .arm,
         .armeb,