staging: rtl8188eu: remove unnecessary call to memset

call to memset to assign 0 value immediately after allocating
memory with kzalloc is unnecesaary as kzalloc allocates the memory
filled with 0 value.

Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>