leds: lgm-sso: Remove unneeded of_match_ptr()

LGM SSO is an OF dependent driver, so of_match_ptr() can be safely
removed.

Remove the unneeded of_match_ptr().

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>