doc: mmc: drop 0x prefixes in read/write examples

The patch drops 0x prefixes because all numbers are interpreted as HEX
by default.

Also, it fixes the mismatch between input arguments and output at 'mmc
write' example. Now it's 256 (0x100) blocks.

Signed-off-by: Alexander Shirokov <shirokovalexs@gmail.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/usage/cmd/mmc.rst b/doc/usage/cmd/mmc.rst
index 55e3f9c..71a0303 100644
--- a/doc/usage/cmd/mmc.rst
+++ b/doc/usage/cmd/mmc.rst
@@ -213,10 +213,10 @@
 The raw data can be read/written via 'mmc read/write' command:
 ::
 
-    => mmc read 0x40000000 0x5000 0x100
+    => mmc read 40000000 5000 100
     MMC read: dev # 0, block # 20480, count 256 ... 256 blocks read: OK
 
-    => mmc write 0x40000000 0x5000 0x10
+    => mmc write 40000000 5000 100
     MMC write: dev # 0, block # 20480, count 256 ... 256 blocks written: OK
 
 The partition list can be shown via 'mmc part' command: