Flash support patch review

[Mori Hiroki]

Hi.

I make two review for flash.

One is cfi write bug fix on mx flash.

https://reviews.freebsd.org/D14279


The other is automatic find rootfs at geom_flashmap.

dts file is set while firmware partition by named "firmware"

Then find rootfs after u-boot image.

This dts file is same as linux it.

https://reviews.freebsd.org/D13648


Please somebody check this review.

Regards

Hiroki Mori