memory: split memory_region_from_host from qemu_ram_addr_from_host

Move the old qemu_ram_addr_from_host to memory_region_from_host and
make it return an offset within the region.  For qemu_ram_addr_from_host
return the ram_addr_t directly, similar to what it was before
commit 1b5ec23 ("memory: return MemoryRegion from qemu_ram_addr_from_host",
2013-07-04).

Reviewed-by: Marc-André Lureau <marcandre.lureau@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index fc609ad..aaee995 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -57,7 +57,7 @@
 
 void qemu_ram_remap(ram_addr_t addr, ram_addr_t length);
 /* This should not be used by devices.  */
-MemoryRegion *qemu_ram_addr_from_host(void *ptr, ram_addr_t *ram_addr);
+ram_addr_t qemu_ram_addr_from_host(void *ptr);
 RAMBlock *qemu_ram_block_by_name(const char *name);
 RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
                                    ram_addr_t *offset);