Remove 2 functions private to the alpha implemetation,
in favor of similar functions in <linux/log2.h>.

Provide a more efficient version of the fls64 function
for pre-ev67 alphas.
Signed-off-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>