Add phosphor-logging to SDK

Other repos need the elog.hpp and log.hpp files, this will
get them into the SDK.

Change-Id: Ibb9316686f12483cef8333fa8a514f1402ee233f
Signed-off-by: Andrew Geissler <andrewg@us.ibm.com>
diff --git a/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend b/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
index b21e2d0..529002c 100644
--- a/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
+++ b/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
@@ -1 +1 @@
-RRECOMMENDS_${PN}_append = " gtest sdbusplus"
+RRECOMMENDS_${PN}_append = " gtest sdbusplus phosphor-logging"