staging/rtl8723bs/core/rtw_ap: Remove redundant call to memset

rtw_zmalloc is internally doing memset . So there is no need to call memset
again.

Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>