ARM: shmobile: Remove KZM9D board code

Get rid of KZM9D board code written in C. This version of the
C board code was used in the case of multiplatform, but these
days DT can be used instead, so because of that simply get rid
of the C code to simplify and save space.

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