openvswitch: switch patch with patch from ovs trunk

After a few discussions with the guys working on OpenVSwitch
they've recommended we use the EXTRA_CFLAGS env var for setting
flags for the kernel module.

They've updated the trunk with a patch to accomodate that.
That patch is also in this commit, and replaces a patch that I proposed.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
openvswitch: use EXTRA_CFLAGS instead of KCFLAGS

The patch we've switched requires EXTRA_CFLAGS to be set instead of KCFLAGS.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Merge pull request #587 from commodo/ovs-patch-update

OpenVSwitch patch update