pinctrl: samsung: drop pin banks references on error paths

The driver iterates over its devicetree children with
for_each_child_of_node() and stores for later found node pointer.  This
has to be put in error paths to avoid leak during re-probing.

Fixes: ab663789 ("pinctrl: samsung: Match pin banks with their device nodes")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Link: https://lore.kernel.org/r/20220111201426.326777-2-krzysztof.kozlowski@canonical.com