ACPI: video: remove dmesg spam

i am actually heavily using the ACPI video extension for my Thinkpad X61
Tablet. I have bound the input events triggered by the brightness
up/down keys to a simple

echo <value> > /sys/class/backlight/acpi_video1/brightness

but everytime the event is triggered and acpi_video_device_lcd_set_level()
is called i got a notificication in my kernel log like:

set_level status: 0
set_level status: 0
set_level status: 0
set_level status: 0
...

Signed-off-by: Maik Broemme <mbroemme@plusserver.de>
Signed-off-by: Len Brown <len.brown@intel.com>