pinctrl: devicetree.c: remove orphan pinctrl_dt_has_hogs()

pinctrl: devicetree.c: remove orphan pinctrl_dt_has_hogs()

The helper pinctrl_dt_has_hogs() was introduced in
99e4f67508e1 (pinctrl: core: Use delayed work for hogs), but the sole
use then got removed shortly after in 950b0d91dc10 (pinctrl: core: Fix
regression caused by delayed work for hogs).

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20190923142005.5632-1-linux@rasmusvillemoes.dk
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>