leds: sun50i-a100: Use match_string() helper to simplify the code

match_string() returns the array index of a matching string.
Use it instead of the open-coded implementation.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20240426152515.872917-1-andriy.shevchenko@linux.intel.com


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