exec: fix guest memory access for Xen

In cpu_physical_memory_rw, a change has been introduced and qemu_get_ram_ptr is
no longuer called with the ram addr we want to access, but only with the
section address. This patch fixes this. (All other call to qemu_get_ram_ptr are
already called with the right address.)

This patch fixes Xen guest.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/exec.c b/exec.c
index a3818ff..265e895 100644
--- a/exec.c
+++ b/exec.c
@@ -3856,8 +3856,8 @@
                 }
             } else {
                 /* RAM case */
-                ptr = qemu_get_ram_ptr(section->mr->ram_addr)
-                    + section_addr(section, addr);
+                ptr = qemu_get_ram_ptr(section->mr->ram_addr
+                                       + section_addr(section, addr));
                 memcpy(buf, ptr, l);
                 qemu_put_ram_ptr(ptr);
             }