pinctrl: st: Remove STiH415/6 SoC pinctrl driver support.

STiH415/6 SoC support is being removed from the kernel.
This patch updates the ST pinctrl driver and removes
references to these obsolete platforms. As some structures
referenced by STiH407 based configuration were shared with
STiH416 we update these names to match the remaining
supported platform.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Cc: <linus.walleij@linaro.org>
Cc: <linux-gpio@vger.kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>