arm64: kexec_file: forbid kdump via kexec_file_load()

Now that kexec_walk_memblock() can do the crash-kernel placement itself
architectures that don't support kdump via kexe_file_load() need to
explicitly forbid it.

We don't support this on arm64 until the kernel can add the elfcorehdr
and usable-memory-range fields to the DT. Without these the crash-kernel
overwrites the previous kernel's memory during startup.

Add a check to refuse crash image loading.
Reviewed-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/kexec_image.c

@@ -47,6 +47,10 @@ static void *image_load(struct kimage *image,
 	struct kexec_segment *kernel_segment;
 	int ret;
 
+	/* We don't support crash kernels yet. */
+	if (image->type == KEXEC_TYPE_CRASH)
+		return ERR_PTR(-EOPNOTSUPP);
+
 	/*
 	 * We require a kernel with an unambiguous Image header. Per
 	 * Documentation/booting.txt, this is the case when image_size