rtl8188eu: new package

[Thomas:
  - remove patches 0001 and 0002, they are not needed since when using
    the kernel-module infrastructure, we directly call the kernel
    build system and bypass the one provided by the external module
  - install the firmware directly in the Buildroot .mk file, which
    allows to also remove patch 0003.
  - remove RTL8188EU_DEPENDENCIES = linux, since this is already
    handled by the kernel-module infrastructure.]

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>