ARM: shmobile: Remove legacy KZM9D board code

Remove the C and platform device version of KZM9D.

The DT version of KZM9D board support can now instead
directly be used with SoC specific code in setup-emev2.c.

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