Make the YAFFS filesystem work

Make the YAFFS filesystem work

Recently the YAFFS filesystem support has been added to U-boot.
However, just enabling CONFIG_YAFFS2 is not enough to get it working.

ymount will generate an exception (when dereferencing mtd->readoob()), because
the genericDevice is a null pointer. Further, a lot of logging is produced
while using YAFFS fs, so logging should also be disabled.
Both issues are solved by this patch.

With this patch and CONFIG_YAFFS2 enabled, I get a readable filesystem
in U-boot, as well as in Linux.

Tested on a Atmel AT91SAM9261EK board.

Signed-off-by: Remy Bohmer <linux@bohmer.net>
Acked-by: William Juul <william.juul@tandberg.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>