common, kconfig: Fix defaut value of BOOTSTAGE_STASH_SIZE

The default value of BOOTSTAGE_STASH_SIZE should be set to hexadecimal,
but an integer value is set. This fixes the BOOTSTAGE_STASH_SIZE number
from hexadecimal to integer.
Signed-off-by: NNobuhiro Iwamatsu <iwamatsu@nigauri.org>

common/Kconfig

@@ -90,7 +90,7 @@ config BOOTSTAGE_STASH_ADDR
 
 config BOOTSTAGE_STASH_SIZE
 	hex "Size of boot timing stash region"
-	default 4096
+	default 0x1000
 	help
 	  This should be large enough to hold the bootstage stash. A value of
 	  4096 (4KiB) is normally plenty.