compat-wireless: backport addr_assign_type usage

compat-wireless: backport addr_assign_type usage

The alx driver uses the addr_assign_type variable from
the netdev data structure which was added as of 2.6.35:

mcgrof@tux ~/linux-next (git::master)$ git describe --contains c1f79426
v2.6.36-rc1~571^2~104

Although compat.git backported dev_hw_addr_random() the patch
in compat.git cannot address usage of addr_assign_type and as
such requires an ifdef around it.

Signed-off-by: Luis R. Rodriguez <mcgrof@frijolero.org>