Revert "Add f16/f128 handling in a couple places"

The f16/f128 handling introduced as part of rust-lang/rustc#125016 (Update
compiler_builtins to 0.1.114) broke compilation on LoongArch and RISC-V:

error: internal compiler error: compiler/rustc_codegen_llvm/src/abi.rs:
126:22: unsupported float: Reg { kind: Float, size: Size(2 bytes) }

thread 'rustc' panicked at compiler/rustc_codegen_llvm/src/abi.rs:126:22:
Box<dyn Any>

This should be resolved with LLVM 19, but we are still on LLVM 18.

Revert 99e6a28 as a temporary workaround.

Ref: rust-lang#125016

compiler/rustc_codegen_llvm/src/abi.rs

@@ -120,10 +120,8 @@ impl LlvmType for Reg {
         match self.kind {
             RegKind::Integer => cx.type_ix(self.size.bits()),
             RegKind::Float => match self.size.bits() {
-                16 => cx.type_f16(),
                 32 => cx.type_f32(),
                 64 => cx.type_f64(),
-                128 => cx.type_f128(),
                 _ => bug!("unsupported float: {:?}", self),
             },
             RegKind::Vector => cx.type_vector(cx.type_i8(), self.size.bytes()),

compiler/rustc_target/src/abi/call/mod.rs

@@ -238,10 +238,8 @@ impl Reg {
                 _ => panic!("unsupported integer: {self:?}"),
             },
             RegKind::Float => match self.size.bits() {
-                16 => dl.f16_align.abi,
                 32 => dl.f32_align.abi,
                 64 => dl.f64_align.abi,
-                128 => dl.f128_align.abi,
                 _ => panic!("unsupported float: {self:?}"),
             },
             RegKind::Vector => dl.vector_align(self.size).abi,