spi flash: fix crash due to spi flash miscommunication

Higher spi flash layers expect to be given back a pointer that was
malloced so that it can free the result, but the lower layers return
a pointer that is in the middle of the malloced memory. Reorder the
members of the lower spi structures so that things work out.

Signed-off-by: Brad Bozarth <bflinux@yumbrad.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>