This commit separates to its own directory the timing code specific
to bere linux implementations.  If you build with ARCH=bare-i386
or ARCH=bare-i386-64, TIME=bare is automatically selected.

Please note how bare builds don't allow externally-set TIME=, as the
architecture Makefile forces "TIME := bare" (not "TIME ?= bare").

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>