wimax/i2400m: remove redundant variables ack_status, bcf and protocol

Variables ack_status, bcf and protocol are being assigned but are
never used hence they are redundant and can be removed.

Also declare ack_type as unsigned int rather than unsigned to clean
up a checkpatch warning.

Cleans up clang warnings:
warning: variable 'ack_status' set but not used [-Wunused-but-set-variable]
warning: variable 'bcf' set but not used [-Wunused-but-set-variable]
warning: variable 'protocol' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>