configs: remove rv1109 support

Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
Change-Id: I529d79c2e2d2344a51714c39375458005d931e38

configs: add README.rockchip

Short introduction of all rockchip platform defconfig.

Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
Change-Id: I44b0621741e1b7fa3243a15e7313546bbd368d21