pinctrl: downgrade pinctrl_get warning when no maps are found

This may be perfectly legitimate. An IP block may get re-used
across SoCs. Not all of those SoCs may need pinmux settings for the
IP block, e.g. if one SoC dedicates pins to that function but
another doesn't. The driver won't know this, and will always
attempt to set up the pinmux. The mapping table defines whether any
HW programming is actually needed.

Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
[rebased to fit the applied patch series]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>