Kconfig: Drop CONFIG_CMD_MEM

This is not actually used in U-Boot. Most likely it means
CONFIG_CMD_MEMORY so change all occurences to that.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/README b/README
index 3735916..01815d4 100644
--- a/README
+++ b/README
@@ -3693,7 +3693,7 @@
 
 - CONFIG_LOOPW
 		Add the "loopw" memory command. This only takes effect if
-		the memory commands are activated globally (CONFIG_CMD_MEM).
+		the memory commands are activated globally (CONFIG_CMD_MEMORY).
 
 - CONFIG_MX_CYCLIC
 		Add the "mdc" and "mwc" memory commands. These are cyclic
@@ -3707,7 +3707,7 @@
 		This command will write 12345678 to address 100 all 10 ms.
 
 		This only takes effect if the memory commands are activated
-		globally (CONFIG_CMD_MEM).
+		globally (CONFIG_CMD_MEMORY).
 
 - CONFIG_SKIP_LOWLEVEL_INIT
 		[ARM, NDS32, MIPS only] If this variable is defined, then certain