omap3: zoom1: disable JFFS2 and enable FS_GENERIC

This is more in line with commits
664979a2(omap3_beagle: remove JFFS2
support.) and 102ce9ea (omap3_beagle:
enable CMD_FS_GENERIC and simplify load of image/ramdisk)

CMD_FS_GENERIC allows us to simplify where we load up our image from
either from ext2/fat etc. So, lets use that instead of cumbersome
options we'd have to use. Sticking with existing conventions,
defaults will be:
bootfile=uImage
bootpart=0:1 (first partition)
bootdir=/ (/ in first partition)

Signed-off-by: Nishanth Menon <nm@ti.com>