ARM: shmobile: marzen: Remove early_printk from command line

As early printk support is not enabled in the kernel in the
shmobile defconfig it does not make much sense to provide for
it in the default command line.

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>