Add mirror u-boot option to obmc-flash-bmc

The mirror u-boot function copies the currently booted BMC chip's u-boot
partition to the alternate chip, if the two don't match. This is to make
sure we always have a good u-boot in the alternate flash.

Also add service file for the mirror u-boot option.

Resolves openbmc/openbmc#2876

Change-Id: Ida09a167de21f3ccb588a096509d88ad88450c93
Signed-off-by: Eddie James <eajames@us.ibm.com>
diff --git a/common/recipes-phosphor/flash/phosphor-software-manager.bb b/common/recipes-phosphor/flash/phosphor-software-manager.bb
index db80ece..43e363b 100644
--- a/common/recipes-phosphor/flash/phosphor-software-manager.bb
+++ b/common/recipes-phosphor/flash/phosphor-software-manager.bb
@@ -80,6 +80,7 @@
     reboot-guard-enable.service \
     reboot-guard-disable.service \
     obmc-flash-bmc-cleanup.service \
+    obmc-flash-bmc-mirroruboot.service \
     "
 
 # Name of the mtd device where the ubi volumes should be created