ARM: shmobile: bockw: add SPI FLASH support

This patch enables Spansion S25FL008K chip on HSPI0

Signed-off-by: Yusuke Goda <yusuke.goda.sx@renesas.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>