ram_addr: tweaks to xen_modified_memory

Invoke xen_modified_memory from cpu_physical_memory_set_dirty_range_nocode;
it is akin to DIRTY_MEMORY_MIGRATION, so set it together with that bitmap.
The remaining call from invalidate_and_set_dirty's "else" branch will go
away soon.

Second, fix the second argument to the function in the
cpu_physical_memory_set_dirty_lebitmap call site.  That function is only used
by KVM, but it is better to be clean anyway.

Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
