ACPICA: Windows compatibility fix: same buffer/string store

Fix a compatibility issue when the same buffer or string is
stored to itself. This has been seen in the field. Previously,
ACPICA would zero out the buffer/string. Now, the operation is
treated as a NOP.

http://bugzilla.acpica.org/show_bug.cgi?id=803

Reported-by: Rezwanul Kabir <Rezwanul_Kabir@Dell.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>