linux-qcom-uki.bb: Fix build error if INITRAMFS_IMAGE undefined

Fix below error seen when INITRAMFS_IMAGE is undefined.

ERROR: Error for linux-qcom-uki.bb:do_configure[depends], dependency
'${@ '${INITRAMFS_IMAGE}:do_image_complete' if d.getVar('INITRAMFS_IMAGE') else ''}' does not contain exactly one ':' character.
Task 'depends' should be specified in the form 'packagename:task'

Signed-off-by: Viswanath Kraleti <quic_vkraleti@quicinc.com>

recipes-kernel/images/linux-qcom-uki.bb

@@ -22,7 +22,12 @@ do_configure[depends] += " \
     systemd-boot:do_deploy \
     virtual/kernel:do_deploy \
     "
-do_configure[depends] += "${@ '${INITRAMFS_IMAGE}:do_image_complete' if d.getVar('INITRAMFS_IMAGE') else ''}"
+
+python __anonymous () {
+    initramfs_image = d.getVar('INITRAMFS_IMAGE')
+    if initramfs_image:
+        d.appendVarFlag('do_configure', 'depends', ' ${INITRAMFS_IMAGE}:do_image_complete')
+}
 
 do_compile() {
     # Construct the ukify command