target/arm: Move TCG-only VFP code into tcg/ subdir

Most of the target/arm/vfp_helper.c file is purely TCG helper code,
guarded by #ifdef CONFIG_TCG.  Move this into a new file in
target/arm/tcg/.

This leaves only the code relating to getting and setting the
FPCR/FPSR/FPSCR in the original file. (Some of this also is
TCG-only, but that needs more careful disentangling.)

Having two vfp_helper.c files might seem a bit confusing,
but once we've finished moving all the helper code out
of the old file we are going to rename it to vfp_fpscr.c.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250221190957.811948-2-peter.maydell@linaro.org

target/arm/tcg/meson.build

@@ -41,6 +41,7 @@ arm_ss.add(files(
   'vec_helper.c',
   'tlb-insns.c',
   'arith_helper.c',
+  'vfp_helper.c',
 ))
 
 arm_ss.add(when: 'TARGET_AARCH64', if_true: files(