mainstone: Fix incorrect key mapping for Enter key.

According to the manual the (5, 5) corresponds to backspace key, and
not Enter key. Linux kernel maps (5, 4) to the enter key. Fixing it up
to match the mapping in the Linux kernel.
Signed-off-by: NVijay Kumar B. <vijaykumar@zilogic.com>
Reviewed-by: NDeepak S. <deepak@zilogic.com>
Message-id: 1475063033-8176-2-git-send-email-vijaykumar@zilogic.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/arm/mainstone.c

@@ -88,7 +88,7 @@ static const struct keymap map[0xE0] = {
      * Matrix position {5,4} and other keys are missing here.
      * TODO: Compare with Linux code and test real hardware.
      */
-    [0x1c] = {5,5}, /* enter (TODO: might be wrong) */
+    [0x1c] = {5,4}, /* enter */
     [0xc8] = {6,0}, /* up */
     [0xd0] = {6,1}, /* down */
     [0xcb] = {6,2}, /* left */