ARM: shmobile: r8a7740: Make r8a7740_meram_workaround() __init

It's called from eva_init() only, which is __init

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>