plat(fvp): use generic image fetching functions

Some generic functions have been provided for fetching prebuilt images -
use these for FVP runs.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Change-Id: I785890c9b0370279230dfd6f71a54bcdc0ebc9c3
diff --git a/run_config/fvp-linux.stress b/run_config/fvp-linux.stress
index 01a23a3..803235d 100644
--- a/run_config/fvp-linux.stress
+++ b/run_config/fvp-linux.stress
@@ -6,8 +6,8 @@
 #
 
 fetch_tf_resource() {
-	kernel_type="fvp-oe-uboot" get_kernel
-	initrd_type="dummy-ramdisk" get_initrd
+	image="kernel" type="fvp-oe-uboot" get_boot_image
+	image="initrd" type="dummy-ramdisk" get_boot_image
 
 	tmp_dir="$(mktempdir)"
 	ln -s "${img_file:?}" "$archive/rootfs.bin"