meta-openpower: openpower-fru-vpd: Add symlink to git

Add a symbolic link to openpower-fru-vpd.bb named _git.bb and set the
preferred version for the recipe for openpower systems.

Change-Id: I8a7d0ea0118c58d56e9fd428df75324f37e46dcf
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/conf/distro/include/openpower-distrovars.inc b/conf/distro/include/openpower-distrovars.inc
index 479e099..2b5c090 100644
--- a/conf/distro/include/openpower-distrovars.inc
+++ b/conf/distro/include/openpower-distrovars.inc
@@ -2,3 +2,5 @@
 DISTRO_FEATURES_FILTER_NATIVE += "openpower"
 DISTRO_FEATURES_FILTER_NATIVESDK += "openpower"
 DISTROOVERRIDES .= ":df-openpower"
+
+PREFERRED_VERSION_openpower-fru-vpd = "1.0"