ARM: shmobile: armadillo800eva-reference: Do not use r8a7740_add_standard_devices_dt()

Now that r8a7740_add_standard_devices_dt() is just a wrapper for
of_platform_populate() call the latter directly.

This is in preparation for removing r8a7740_add_standard_devices_dt().

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>