powerpc: Make dummy section a valid note header

We are declaring the dummy section (used to work around a binutils
bug) as PT_NOTE, but we don't have enough bytes for it to be a valid
note header, and kexec userspace complains:

Warning: Elf Note name is not null terminated
Warning: append= option is not passed. Using the first kernel root partition
Warning: Elf Note name is not null terminated

Instead of using the arbitray value 0xf177 (aka "fill"), declare a
no-name no-description note of type 0.
Signed-off-by: NMilton Miller <miltonm@bga.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/vmlinux.lds.S

@@ -87,7 +87,9 @@ SECTIONS
 	/* The dummy segment contents for the bug workaround mentioned above
 	   near PHDRS.  */
 	.dummy : AT(ADDR(.dummy) - LOAD_OFFSET) {
-		LONG(0xf177)
+		LONG(0)
+		LONG(0)
+		LONG(0)
 	} :kernel :dummy
 
 /*