pinctrl: ns2: rename pinctrl_utils_dt_free_map

A conflict of two patches caused a build error when a function got renamed
but a new user appeared in the other patch:

drivers/pinctrl/bcm/pinctrl-ns2-mux.c:540:17: error: 'pinctrl_utils_dt_free_map' undeclared here (not in a function)
  .dt_free_map = pinctrl_utils_dt_free_map,
                 ^~~~~~~~~~~~~~~~~~~~~~~~~

This renames the new user of pinctrl_utils_dt_free_map accordingly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: d32f7fd3 ("pinctrl: Rename pinctrl_utils_dt_free_map to pinctrl_utils_free_map")
Fixes: b5aa1006 ("pinctrl: ns2: add pinmux driver support for Broadcom NS2 SoC")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>