staging: comedi: amplc_pci224: omit '!= 0' from logical expressions

Since anything non-zero is logically "true", don't bother doing
"not-equal" comparisons with zero, except when testing for an explicit
number 0 (not as a result of bit tests for example).

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>