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>