blk: Make block subsystems select BLK

blk: Make block subsystems select BLK

The BLK symbol has a few meanings, one of which is that it controls the
driver model portion of a "block device". Rather than having this hidden
symbol be "default y if ..." it should be select'd by the various block
subsystems. Symbols such as PVBLOCK which already select'd BLK are
unchanged".

Reviewed-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Tom Rini <trini@konsulko.com>