iio: light: opt3001: trivial type refactoring

Change variable type of struct opt3001 members 'ok_to_ignore_lock' and
'result_ready' uint16-bitfield of length one to bool.

They are used as bool, let the compiler do the optimization.

Signed-off-by: Alexander Koch <mail@alexanderkoch.net>
Signed-off-by: Michael Hornung <mhornung.linux@gmail.com>
Tested-by: Andreas Dannenberg <dannenberg@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>