make dos partition support default yes if we have disk partition support
DOS partitions are the only partitions we handle at the moment
and without it most MMC/SD enabled configs are useless, so make
it default yes. Also, use 'depends on' instead of 'if'
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Juergen Beisert <jbe@pengutronix.de>