leds: lm3642: rename devAttr to avoid CamelCase

Fixed the checkpatch warning as below:

  WARNING: Avoid CamelCase: <devAttr>

Rename devAttr to attr.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
1 file changed