leds: leds-blinkm: Remove unused variable 'ret'

Function returns void anyway.

Fixes the following W=1 kernel build warning(s):

 drivers/leds/leds-blinkm.c: In function ‘blinkm_init_hw’:
 drivers/leds/leds-blinkm.c:483:6: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]

Cc: Jan-Simon Moeller <jansimon.moeller@gmx.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Jan-Simon Möller" <dl9pf@gmx.de>
Cc: linux-leds@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>