ARM: shmobile: Get rid of legacy KZM9D defconfig

Get rid of the kzm9d_defconfig. The KZM9D is now supported
as DT only in case of EMEV2 is selected in the kernel
configuration.

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