staging: rtl8192u: r8192U_core.c: Fix to remove null pointer checks that could never happen

Removal of null pointer checks that could never happen

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>