leds: trigger: gpio: Use sysfs_emit() to instead of s*printf()

Follow the advice of the Documentation/filesystems/sysfs.rst and show()
should only use sysfs_emit() or sysfs_emit_at() when formatting the
value to be returned to user space.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20231103195310.948327-3-andriy.shevchenko@linux.intel.com


Signed-off-by: Lee Jones <lee@kernel.org>