leds:lp55xx: fix firmware loading error

LP55xx driver uses not firmware file but raw data to load program through
the firmware interface.(Documents/leds/leds-lp55xx.txt)

  For example, here is how to run blinking green channel pattern.
  (The second engine is seleted and MUX is mapped to 'RGB' mode)
  echo 2 > /sys/bus/i2c/devices/xxxx/select_engine
  echo "RGB" > /sys/bus/i2c/devices/xxxx/engine_mux
  echo 1 > /sys/class/firmware/lp5562/loading
  echo "4000600040FF6000" > /sys/class/firmware/lp5562/data
  echo 0 > /sys/class/firmware/lp5562/loading
  echo 1 > /sys/bus/i2c/devices/xxxx/run_engine

However, '/sys/class/firmware/<device name>' is not created after the
firmware loader user helper was introduced.
This feature is used in the case below.

  As soon as the firmware download is requested by the driver, firmware
  class subsystem tries to find the binary file.
  If it gets failed, then it just falls back to user helper to load
  raw data manually. Here, you can see the device file under
  /sys/class/firmware/.

To make it happen, LP55xx driver requires two configurations.

  1. Enable CONFIG_FW_LOADER_USER_HELPER_FALLBACK in Kconfig
  2. Set option, 'FW_OPT_USERHELPER' on requesting the firmware data.
     It means the second option should be 'false' in
     request_firmware_nowait().
     This option enables to load firmware data manually by calling
     fw_load_from_user_helper().

Cc: linux-leds@vger.kernel.org
Signed-off-by: Milo Kim <milo.kim@ti.com>
Acked-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>