linux-imx: Adapt comment to to new override syntax

recipes-kernel/linux/linux-imx_5.15.bb

@@ -17,7 +17,7 @@ SRCREV = "${AUTOREV}"
 # branch= combined with nobranch=1 looks weird, but the branch is used for the
 # AUTOREV, the nobranch tells the fetcher to not check the SHA validation for the branch
 # This way the SRCREV can be specified to a specific revision also outside that branch
-# with SRCREV_pn-linux-guf =
+# with SRCREV:pn-linux-guf =
 SRC_URI = " \
     git://git.seco.com/seco-ne/kernel/linux-imx-kuk.git;protocol=https;branch=linux-${PV}-seco;nobranch=1 \
     file://defconfig \