drivers/misc/bh1770glc.c: error handling in bh1770_power_state_store()

There was a signedness bug so "ret" was never less than zero and that
breaks the error handling.  Also in the original code it would overwrite
ret and the result is still negative but it's bogus number instead of the
correct error code.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Cc: Samu Onkalo <samu.p.onkalo@nokia.com>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>