cputlb: Merge and move memory_notdirty_write_{prepare,complete}

cputlb: Merge and move memory_notdirty_write_{prepare,complete}

Since 9458a9a1df1a, all readers of the dirty bitmaps wait
for the rcu lock, which means that they wait until the end
of any executing TranslationBlock.

As a consequence, there is no need for the actual access
to happen in between the _prepare and _complete.  Therefore,
we can improve things by merging the two functions into
notdirty_write and dropping the NotDirtyInfo structure.

In addition, the only users of notdirty_write are in cputlb.c,
so move the merged function there.  Pass in the CPUIOTLBEntry
from which the ram_addr_t may be computed.

Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>