block: Update BLK to be def_bool

At this point in the DM migration, all platforms enable DM. BLK requires
DM. Make BLK "def_bool y" in the cases it had been "default y" to make
this clearer. Now remove the symbol requirement from other places as it
is redundant here.

Signed-off-by: Tom Rini <trini@konsulko.com>
3 files changed