leds: ti-lmu-common: Move static keyword to the front of declaration

Move the static keyword to the front of declaration of ramp_table,
and resolve the following compiler warning that can be seen when
building with warnings enabled (W=1):

drivers/leds/leds-ti-lmu-common.c:14:1: warning:
  ‘static’ is not at beginning of declaration [-Wold-style-declaration]

Signed-off-by: Krzysztof Wilczynski <kw@linux.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>