drivers/video/backlight/adp8870_bl.c: add missing braces

Add missing braces to include error message.  The error message is
related to the return value for sysfs_create_group().  However,
sysfs_create_group() is called when pdata->en_ambl_sens is not zero.
Thus, the checking return value should be included in the if statement.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>