atlas6 is a SoC very similar with primaII, the register layput of
pinctrl is same, but the pads, groups and functions of atlas6 have
different layout with prima2, this patch
1. pull the definition of pads, groups and functions out of the
pinctrl-sirf driver,and put them into soc-specific files
2. add pads, groups and functions tables for atlas6
3. let pads, groups and functions tables become the config data of
   the related dt compatible node, so the pinctrl-sirf can support
   all SiRF SoCs with the config data as private data.

In this patch,we create a sirf dir, and let
the old drivers/pinctrl/pinctrl-sirf.c =
        drivers/pinctrl/sirf/pinctrl-prima2.c +
        drivers/pinctrl/sirf/pinctrl-sirf.c

drivers/pinctrl/sirf/pinctrl-atlas6.c is a newly created file for the
pin layout of atlas6.
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>