treewide: reduce append operators on SRC_URI

In a base bb file where we are setting the primary git repository, it
is rare that we need to `SRC_URI +=`.  This is an unnecessary pattern
that seems to have been copied throughout the repository.  Remove the
pattern where appropriate and simply set SRC_URI directly.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I430186a82f9582ba6196f5bf66b659af4092b48d
diff --git a/meta-ibm/recipes-phosphor/logging/ibm-logging_git.bb b/meta-ibm/recipes-phosphor/logging/ibm-logging_git.bb
index 6751bcd..441ca8e 100644
--- a/meta-ibm/recipes-phosphor/logging/ibm-logging_git.bb
+++ b/meta-ibm/recipes-phosphor/logging/ibm-logging_git.bb
@@ -5,7 +5,7 @@
 HOMEPAGE = "https://github.com/openbmc/ibm-logging"
 LICENSE = "Apache-2.0"
 LIC_FILES_CHKSUM = "file://${S}/LICENSE;md5=86d3f3a95c324c9479bd8986968f4327"
-SRC_URI += "git://github.com/openbmc/ibm-logging;branch=master;protocol=https"
+SRC_URI = "git://github.com/openbmc/ibm-logging;branch=master;protocol=https"
 SRCREV = "35262538d2b3810f2d168ff76f6d64e77e031ea4"
 
 inherit autotools