pinctrl: amd: Fix an unused variable

`char *output_enable` is no longer used once switching to unicode
output.

Fixes: e8129a07 ("pinctrl: amd: Use unicode for debugfs output")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20220801144952.141-1-mario.limonciello@amd.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>