target/arm: Rearrange cpu64.c so all the CPU initfns are together

target/arm: Rearrange cpu64.c so all the CPU initfns are together

cpu64.c has ended up in a slightly odd order -- it starts with the
initfns for most of the models-real-hardware CPUs; after that comes a
bunch of support code for SVE, SME, pauth and LPA2 properties.  Then
come the initfns for the 'host' and 'max' CPU types, and then after
that one more models-real-hardware CPU initfn, for a64fx.  (This
ordering is partly historical and partly required because a64fx needs
the SVE properties.)

Reorder the file into:
 * CPU property support functions
 * initfns for real hardware CPUs
 * initfns for host and max
 * class boilerplate

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>