meta-phosphor: dbus-interfaces: use assignment operator

Use the assignment operator instead of appending when setting SRC_URI in
a recipe.

Appending to variables without a default such as SRC_URI in this context
is nonsensical and a distraction (granted a minor one) for anyone
accustomed to looking at bitbake metadata.

Perhaps more importantly it confuses tools like devtool.

(From meta-phosphor rev: 10862f2d1890435270651acd8448abca33b7419f)

Change-Id: I9a0fbc3c731499d7f6075c15ff56f24fe0e3d65b
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb b/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb
index 4b617f7..cd9df65 100644
--- a/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb
+++ b/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb
@@ -13,7 +13,7 @@
 DEPENDS += "autoconf-archive-native"
 DEPENDS += "sdbus++-native"
 
-SRC_URI += "git://github.com/openbmc/phosphor-dbus-interfaces"
+SRC_URI = "git://github.com/openbmc/phosphor-dbus-interfaces"
 SRCREV = "6e7634da912cd16c73bc762bf91039179360a0e2"
 
 DEPENDS_remove_class-native = "sdbus++-native"