rpi-cmdline: remove unnecessary spaces from cmdline.txt

With current recipe formatting CMDLINE variable contains
many unnecessary white spaces. This patch allow to drop
unnecessary spaces at the moment of writing them to
cmdline.txt. This will improve readability of cmdline.txt,
/proc/cmdline and dmesg output.

Signed-off-by: Bartłomiej Burdukiewicz <bartlomiej.burdukiewicz@gmail.com>
(cherry picked from commit f5fe02c30c)
Signed-off-by: Ricardo Salveti <ricardo@foundries.io>

recipes-bsp/bootfiles/rpi-cmdline.bb

@@ -37,7 +37,7 @@ CMDLINE = " \
     "
 
 do_compile() {
-    echo "${CMDLINE}" > "${WORKDIR}/cmdline.txt"
+    echo "${@' '.join('${CMDLINE}'.split())}" > "${WORKDIR}/cmdline.txt"
 }
 
 do_deploy() {