lcdc_ld9040: fix locking in lcd_sysfs_store_auto_brightness()

  * mutex was unlocked before the call to lcdc_ld9040_set_brightness()

Change-Id: I73765ca66f3dce908f93290d0e76da8e72c1d2ae
Use lowmemorykiller.c from pre 04-24 kernel

Change-Id: Idbef2578cd31f8b74dbf153ce0b5f6a0e8002416