defconfig: k2l_evm_defconfig: enable net driver model

enable net driver model for k2l evm as keystone_net supports
driver model

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>