s390x/mmu_helper: move address validation into mmu_translate*()

s390x/mmu_helper: move address validation into mmu_translate*()

Let's move address validation into mmu_translate() and
mmu_translate_real(). This allows for checking whether an absolute
address is valid before looking up the storage key. We can now get rid of
the ram_size check.

Interestingly, we're already handling LOAD REAL ADDRESS wrong, because
a) We're not supposed to touch storage keys
b) We're not supposed to convert to an absolute address

Let's use a fake, negative MMUAccessType to teach mmu_translate() to
fix that handling and to not perform address validation.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20210903155514.44772-8-david@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>