Revert "backlight: fix memory leak on obscure error path"

This reverts commit 9ea3c498

.

'data' is being allocated by devm_kzalloc(), is it's actually
wrong to free() it in the error path, as it will be destroyed
properly later.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>