tcg: Compress TCGLabelQemuLdst

Use 1 32-bit word instead of 6.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-aarch64: Use 32-bit loads for qemu_ld_i32

The "old" qemu_ld opcode did not specify the size of the result,
and so we had to assume full register width.  With the new opcodes,
we can narrow the result.

Signed-off-by: Richard Henderson <rth@twiddle.net>