exec/cpu: Make host pages variables / macros 'target agnostic'

exec/cpu: Make host pages variables / macros 'target agnostic'

"host" pages are related to the *host* not the *target*,
thus the qemu_host_page_size / qemu_host_page_mask variables
and the HOST_PAGE_ALIGN() / REAL_HOST_PAGE_ALIGN() macros
can be moved to "exec/cpu-common.h" which is target agnostic.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20220120000836.229419-1-f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>