ALPHA: correct low-level I/O routines for sable-lynx

This code corrects the behavior of the t2_readX/t2_writeX routines,
and t2_ioreadNN/t2_iowriteNN routines.

The value T2_DENSE_MEM is now subtracted from the "xaddr" argument in
each of the readX/writeX routines, since those routines may be called
directly, rather than always through the ioreadNN/iowriteNN routines.

Examples of the direct calls, via the __raw_readX/writeX macros, are
the memcpy_fromio/toio, _memset_c_io, and scr_memcpyw routines.

Signed-off-by: Jay Estabrook <jay.estabrook@hp.com>
Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>