Staging: rtl8723bs: core: remove set but not used 'ptxservq'

Fix the following gcc warning:

drivers/staging/rtl8723bs/core/rtw_sta_mgt.c:556:19: warning: variable
‘ptxservq’ set but not used [-Wunused-but-set-variable]
  struct tx_servq *ptxservq;
                   ^~~~~~~~

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200427032342.27211-4-yanaijie@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>