target/ppc: Prohibit target specific KVM prototypes on user emulation

target/ppc: Prohibit target specific KVM prototypes on user emulation

None of these target-specific prototypes should be used
by user emulation. Remove their declaration there, so we
get a compile failure if ever used (instead of having to
deal with linker and its possible optimizations, such
dead code removal).

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20231003070427.69621-5-philmd@linaro.org>