The time operations are get, set and adjust. They are methods of a
single structure in order to simplify use of custom timers (and make
them separate works according to the LGPL).

This patch set introduces specific <arch>-time.c files where all the
timing stuff lives (not much, actually). Sometimes this turns
<arch>-io.c into an almost-empty file, but that how history changes
stuff.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>