powerpc: Add comment explaining the purpose of setup_kdump_trampoline()

Anything in early_setup() needs to be justified to be there, in
this case, we need the trampolines before we can take exceptions
and thus before we turn on the MMU.

Also remove a pretty meaningless and misplaced debug message
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
[mpe: Fix comment formatting]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/setup_64.c

@@ -279,10 +279,12 @@ void __init early_setup(unsigned long dt_ptr)
 	/* Probe the machine type */
 	probe_machine();
 
+	/*
+	 * Setup the trampolines from the lowmem exception vectors
+	 * to the kdump kernel when not using a relocatable kernel.
+	 */
 	setup_kdump_trampoline();
 
-	DBG("Found, Initializing memory management...\n");
-
 	/* Initialize the hash table or TLB handling */
 	early_init_mmu();