alpha: Remove set but unused variables.

This is a new warning in gcc 4.6.  Several of these variables are
used within #if 0 code, which probably ought to be removed.  Most
of the changes are legitimate cleanups.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>