ARM: shmobile: lager-reference: Enable multiplaform kernel support

Enable multiplaform ARM architecture support for the Lager reference
board. Common clock framework initialization will be handled by the
rcar_gen2_init_timer() call, we just need to remove the legacy clock
code initialization.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>