staging: ccree: remove compare to none zero

The driver was full of code checking "if (x != 0)".
Replace by "if (x)" for better readability.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>