staging: comedi: amplc_pci230: replace `state` member with bitfields

The `state` member of `struct pci230_private` is used with the atomic
bit-op functions and has a couple of bits defined, `AI_CMD_STARTED` and
`AO_CMD_STARTED`.  Spin-locks are used to protect the clearing of these
bits and other stuff.  No special protection is used for setting these
bits.  Replace the `state` member with a couple of new, single-bit
bitfield members, `ai_cmd_started` and `ao_cmd_started` to save some
space.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>