mrw-rev.bbclass: bump version

Change-Id: Ib78452fd969b0b2718551a8ff1b6a279624ceb6a
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/classes/mrw-rev.bbclass b/classes/mrw-rev.bbclass
index bcce6dc..c555721 100644
--- a/classes/mrw-rev.bbclass
+++ b/classes/mrw-rev.bbclass
@@ -2,4 +2,4 @@
 MRW_API_SRCREV ?= "60c8e10cbb11768cd1ba394b35cb1d6627efec42"
 
 MRW_TOOLS_SRC_URI ?= "git://github.com/openbmc/phosphor-mrw-tools"
-MRW_TOOLS_SRCREV ?= "8b34b33ffa0c60e12284a190dd4d59fc695a4018"
+MRW_TOOLS_SRCREV ?= "312fa6baba47e6a6fa9001f577d2a8993e148dc9"