sysemu/kvm: Restrict kvmppc_get_radix_page_info() to ppc targets

sysemu/kvm: Restrict kvmppc_get_radix_page_info() to ppc targets

kvm_get_radix_page_info() is only defined for ppc targets (in
target/ppc/kvm.c). The declaration is not useful in other targets,
reduce its scope.
Rename using the 'kvmppc_' prefix following other declarations
from target/ppc/kvm_ppc.h.

Suggested-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20231003070427.69621-2-philmd@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>