staging: r8188eu: replace rtw_malloc/copy_from_user sequence with memdup_user

memdup_user is shorter and expressively.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Link: https://lore.kernel.org/r/20200412173716.846469-1-insafonov@gmail.com


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