npcm7xx-emc: diorite c0 workaround

Remove garbage byte sent by c0 and re-calculate checksum.
This assumes that there are always 1 byte garbage, which is the case
based on current testing.

Change-Id: I92465e3350ce606e288853ea040ba2be88a99e8f
Signed-off-by: Yuxiao Zhang <yuxiaozhang@google.com>
(cherry picked from commit 90f2cffc710aafb6ceec75bf0d7503506fbaaed5)
(cherry picked from commit 141daea52e9e3ffad6db25bac24f404d1726fcfa)