mmc: Add dependency to openpower-update-bios-attr-table.service

The openpower-update-bios-attr-table.service creates symlinks to lid
files is the partition files do not exist. The service
openpower-process-host-firmware.service creates symlinks to the well
known firmware name by deleting the base partition file and creting a
symlink. If both services run at the same time, they can interfere,
causing the bios attr service to create a symlink when it's not desired
(it thinks the file doesn't exist but it's because the process host fw
service just deleted it to create its symlink). Add a dependency to
serialize them.

Tested:
Before fix:
Sep 17 14:18:35 p10bmc systemd[1]: Starting Set POWER host firmware well-known names...
Sep 17 14:18:35 p10bmc systemd[1]: Starting Update BIOS attr table with host firmware well-known names...
Sep 17 14:18:35 p10bmc openpower-update-manager[2026]: "/media/hostfw/running/DEVTREE": File exists
Sep 17 14:18:35 p10bmc systemd[1]: openpower-process-host-firmware.service: Deactivated successfully.
Sep 17 14:18:35 p10bmc systemd[1]: Finished Set POWER host firmware well-known names.
Sep 17 14:18:35 p10bmc systemd[1]: openpower-update-bios-attr-table.service: Deactivated successfully.
Sep 17 14:18:35 p10bmc systemd[1]: Finished Update BIOS attr table with host firmware well-known names.

After fix:
Sep 17 14:19:26 p10bmc systemd[1]: Starting Set POWER host firmware well-known names...
Sep 17 14:19:26 p10bmc systemd[1]: openpower-process-host-firmware.service: Deactivated successfully.
Sep 17 14:19:26 p10bmc systemd[1]: Finished Set POWER host firmware well-known names.
Sep 17 14:19:26 p10bmc systemd[1]: Starting Update BIOS attr table with host firmware well-known names...
Sep 17 14:19:26 p10bmc systemd[1]: openpower-update-bios-attr-table.service: Deactivated successfully.
Sep 17 14:19:26 p10bmc systemd[1]: Finished Update BIOS attr table with host firmware well-known names.

Change-Id: I3bc0366a38676d391e1087c27f2fcff487ac5914
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/mmc/openpower-update-bios-attr-table.service b/mmc/openpower-update-bios-attr-table.service
index 66c0b22..898cb7e 100644
--- a/mmc/openpower-update-bios-attr-table.service
+++ b/mmc/openpower-update-bios-attr-table.service
@@ -2,6 +2,7 @@
 Description=Update BIOS attr table with host firmware well-known names
 After=org.open_power.Software.Host.Updater.service
 After=obmc-flash-bios-init.service
+After=openpower-process-host-firmware.service
 
 [Service]
 Type=oneshot