exec: Simplify the guest physical memory allocation hook

Make it a generic hook rather than a KVM hook.  Less code and
ifdeffery.

Since the only user of the hook is old S390 KVM, there's hope we can
get rid of it some day.

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: 1375276272-15988-5-git-send-email-armbru@redhat.com
Signed-off-by: Anthony Liguori <anthony@codemonkey.ws>
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index beb4149..77242e2 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -368,6 +368,8 @@
 
 #if !defined(CONFIG_USER_ONLY)
 
+void phys_mem_set_alloc(void *(*alloc)(ram_addr_t));
+
 struct MemoryRegion *iotlb_to_region(hwaddr index);
 bool io_mem_read(struct MemoryRegion *mr, hwaddr addr,
                  uint64_t *pvalue, unsigned size);