cmd_mem: localize state variables

These "last" variables aren't used outside of this file, so add static.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/cmd_mem.c b/common/cmd_mem.c
index f7a442a..f03233c 100644
--- a/common/cmd_mem.c
+++ b/common/cmd_mem.c
@@ -48,9 +48,9 @@
 /* Display values from last command.
  * Memory modify remembered values are different from display memory.
  */
-uint	dp_last_addr, dp_last_size;
-uint	dp_last_length = 0x40;
-uint	mm_last_addr, mm_last_size;
+static uint	dp_last_addr, dp_last_size;
+static uint	dp_last_length = 0x40;
+static uint	mm_last_addr, mm_last_size;
 
 static	ulong	base_address = 0;