[PATCH] swiotlb: file header comments

Change comment at top of swiotlb.c to reflect that the code is shared
with EM64T (i.e. Intel x86_64). Also add an entry for myself so that
if I "broke it", everyone knows who "bought it"... :-)

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>