Staging: rtlwifi: Cleanup crc16_ccitt()

crc16_ccitt() function does "BIT(0) << i" instead of "BIT(i)".
Using !! is slightly shorter than "foo ? 1: 0" and remove unnecessary
parentheses to make the code simple.

Issue suggested by Coccinelle.

Signed-off-by: Madhumitha Prabakaran <madhumithabiw@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>