MIPS: Loongson: Fix LOONGSON_ADDRWIN_CFG macro.

There's a typo in the LOONGSON_ADDRWIN_CFG macro. The cpu window mmap
register address should contain the destination parameters not the
source one.  This has not been noticed because the code is only using
source = destination.

Signed-off-by: Arnaud Patard <apatard@mandriva.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/1162/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>