staging: rtl8723bs: core: rtw_sta_mgt: Remove unused variable 'psta'

staging: rtl8723bs: core: rtw_sta_mgt: Remove unused variable 'psta'

Fixes the following W=1 kernel build warning(s):

 drivers/staging/rtl8723bs/core/rtw_sta_mgt.c: In function ‘kfree_all_stainfo’:
 drivers/staging/rtl8723bs/core/rtw_sta_mgt.c:128:19: warning: variable ‘psta’ set but not used [-Wunused-but-set-variable]

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ross Schmidt <ross.schm.dev@gmail.com>
Cc: linux-staging@lists.linux.dev
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210414181129.1628598-17-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>