gpio: tegra: Clean-up debugfs initialisation

The function tegra_gpio_debuginit() just calls debugfs_create_file()
and given that there is already a stub function implemented for
debugfs_create_file() when CONFIG_DEBUG_FS is not enabled, there is
no need for the function tegra_gpio_debuginit() and so remove it.

Finally, use a space and not a tab between the #ifdef and
CONFIG_DEBUG_FS.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>