ARM: shmobile: armadillo800eva reference: Remove C board code

Now when the r8a7740 generic multiplatform case has the same
features as the DT reference board code then get rid of the
Armadillo800EVA DT reference C board code. DT Reference code
in the future shall make use of the r8a7740 Multiplatform
support code with the generic SoC machine vector.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>