as refer in this patch "arm & sh: factorised duplicated clkdev.c"

factorise some generic infrastructure to assist looking up struct clks
for the ARM & SH architecture.

as the code is identical at 99% in linux

move it also as preparing for the SH adding

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>