ARM: shmobile: r8a7740: Remove unused r8a7740_add_early_devices_dt()

It was removed in commit 744fdc8d ("ARM:
shmobile: r8a7740: Prepare for reference DT setup"), but accidentally
resurrected in commit 88378837 ("ARM:
shmobile: Remove unused r8a7740 auxdata table").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>