buildroot

configs: warpboard: Move to kernel version 4.4.15

Currently warpboard uses a 4.0.5 kernel version from github.

Move to version 4.4.15, which is a long term supported kernel version.

With 4.4.15 we no longer need the extra two kernel patches as they have
already been upstreamed.

Use a linux fragment file, so that wireless can be functional by default.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>