disas: Fix build against Capstone v6

disas: Fix build against Capstone v6

Capstone v6 made major changes, such as renaming for AArch64, which
broke programs using the old headers, like QEMU. However, Capstone v6
provides the CAPSTONE_AARCH64_COMPAT_HEADER compatibility definition
allowing to build against v6 with the old definitions, so fix the QEMU
build using it.

We can lift that definition and switch to the new naming once our
supported distros have Capstone v6 in place.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Link: https://lore.kernel.org/r/20240715213943.1210355-1-gustavo.romero@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>