staging: rtlwifi: base: Remove set but not used variables

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/staging/rtlwifi/base.c: In function 'rtl_tx_agg_stop':
drivers/staging/rtlwifi/base.c:1733:23: warning:
 variable 'tid_data' set but not used [-Wunused-but-set-variable]

drivers/staging/rtlwifi/base.c: In function 'rtl_check_beacon_key':
drivers/staging/rtlwifi/base.c:2474:5: warning:
 variable 'ds_param_len' set but not used [-Wunused-but-set-variable]

drivers/staging/rtlwifi/base.c:2472:5: warning:
 variable 'ht_oper_len' set but not used [-Wunused-but-set-variable]

drivers/staging/rtlwifi/base.c:2470:5: warning:
 variable 'ht_cap_len' set but not used [-Wunused-but-set-variable]

They are never used and can be removed.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>