qca-ssdk: use OpenWrt GIT repo as upstream

qca-ssdk: use OpenWrt GIT repo as upstream

Instead of having to deal with patch files, lets use the newly made
OpenWrt GIT repo as the SSDK upstream[1].

All existing patches have been applied to the same source commit, so
there should be no intended changes.

[1] https://github.com/openwrt/qca-ssdk.git

Signed-off-by: Robert Marko <robimarko@gmail.com>