gpio: mockup: Fix potential resource leakage when register a chip

gpio: mockup: Fix potential resource leakage when register a chip

commit 02743c4091ccfb246f5cdbbe3f44b152d5d12933 upstream.

If creation of software node fails, the locally allocated string
array is left unfreed. Free it on error path.

Fixes: 6fda593f3082 ("gpio: mockup: Convert to use software nodes")
Cc: stable@vger.kernel.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>