pinctrl: fix pinmux_hog_maps when ctrl_dev_name is not set

The ctrl_dev_name is optional for struct pinmux_map assuming
that ctrl_dev is set. Without this patch we can get:

Unable to handle kernel NULL pointer dereference at virtual
address 00000000
...
(pinmux_hog_maps+0xa4/0x20c)
(pinctrl_register+0x2a4/0x378)
...

Fix this by adding adding a test for map->ctrl_dev.
Additionally move the test for map->ctrl_dev earlier
to optimize out the loop a bit.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>