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-openpower/recipes-bsp/fsidbg/fsidbg_git.bb b/meta-openpower/recipes-bsp/fsidbg/fsidbg_git.bb
index b652ad5..4a38ba4 100644
--- a/meta-openpower/recipes-bsp/fsidbg/fsidbg_git.bb
+++ b/meta-openpower/recipes-bsp/fsidbg/fsidbg_git.bb
@@ -3,7 +3,7 @@
 LICENSE     = "GPLv3"
 LIC_FILES_CHKSUM = "file://${S}/LICENSE;md5=84dcc94da3adb52b53ae4fa38fe49e5d"
 
-SRC_URI += "git://github.com/eddiejames/fsidbg.git;branch=master;protocol=https"
+SRC_URI = "git://github.com/eddiejames/fsidbg.git;branch=master;protocol=https"
 
 SRCREV = "dfe278065c877724242dfae15a4c627fd2e3611c"
 PV = "git${SRCREV}"