Consolidate bootcount code into drivers/bootcount

Consolidate bootcount code into drivers/bootcount

This patch moves all bootcount implementations into a common
directory: drivers/bootcount. The generic bootcount driver
is now usable not only by powerpc platforms, but others as well.

Signed-off-by: Stefan Roese <[email protected]>
Cc: Heiko Schocher <[email protected]>
Cc: Valentin Longchamp <[email protected]>
Cc: Christian Riesch <[email protected]>
Cc: Manfred Rudigier <[email protected]>
Cc: Mike Frysinger <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Reinhard Meyer <[email protected]>
Tested-by: Valentin Longchamp <[email protected]>
Tested-by: Christian Riesch <[email protected]>
Acked-by: Rob Herring <[email protected]>
Acked-by: Mike Frysinger <[email protected]>