seeds: add seed for OMAP1 only builds

this will help us catch build errors on OMAP1
kernel builds.

Signed-off-by: Felipe Balbi <balbi@ti.com>
seeds: add MULTI_V6 to seeds too

since ARMv6 supports multiplatform builds,
let's have that enabled.

Signed-off-by: Felipe Balbi <balbi@ti.com>