exec: Drop incorrect & dead S390 code in qemu_ram_remap()

Old S390 KVM wants guest RAM mapped in a peculiar way.  Commit 6b02494
implemented that.

When qemu_ram_remap() got added in commit cd19cfa, its code carefully
mimicked the allocation code: peculiar way if defined(TARGET_S390X) &&
defined(CONFIG_KVM), else normal way.

For new S390 KVM, we actually want the normal way.  Commit fdec991
changed qemu_ram_alloc_from_ptr() accordingly, but forgot to update
qemu_ram_remap().  If qemu_ram_alloc_from_ptr() maps RAM the normal
way, but qemu_ram_remap() remaps it the peculiar way, remapping
changes protection and flags, which it shouldn't.

Fortunately, this can't happen, as we never remap on S390.

Replace the incorrect code with an assertion.

Thanks to Christian Borntraeger for help with assessing the bug's
(non-)impact.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Message-id: 1375276272-15988-6-git-send-email-armbru@redhat.com
Signed-off-by: Anthony Liguori <anthony@codemonkey.ws>
