Change default value of CONFIG_DEBUG_BLOCK_EXT_DEVT to 'n'

It's a debug option that you would explicitly enable to test this
feature, we should default it to 'n' to prevent accidental surprises
for now.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5a536f7..4378d5e 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -628,7 +628,7 @@
         bool "Force extended block device numbers and spread them"
 	depends on DEBUG_KERNEL
 	depends on BLOCK
-	default y
+	default n
 	help
 	  Conventionally, block device numbers are allocated from
 	  predetermined contiguous area.  However, extended block area