dm: fix Kconfig indentation

Since DM_DEBUG_BLOCK_STACK_TRACING is a DM_PERSISTENT_DATA config option
move it from drivers/md/Kconfig to drivers/md/persistent-data/Kconfig.

Doing so fixes indentation for other DM config options.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/Kconfig

@@ -254,16 +254,6 @@ config DM_THIN_PROVISIONING
        ---help---
          Provides thin provisioning and snapshots that share a data store.
 
-config DM_DEBUG_BLOCK_STACK_TRACING
-	boolean "Keep stack trace of persistent data block lock holders"
-	depends on STACKTRACE_SUPPORT && DM_PERSISTENT_DATA
-	select STACKTRACE
-	---help---
-	  Enable this for messages that may help debug problems with the
-	  block manager locking used by thin provisioning and caching.
-
-	  If unsure, say N.
-
 config DM_CACHE
        tristate "Cache target (EXPERIMENTAL)"
        depends on BLK_DEV_DM