powerpc/8xx: fix setting of pagetable for Abatron BDI debug tool.

[ Upstream commit fb0bdec51a4901b7dd088de0a1e365e1b9f5cd21 ]

Commit 8c8c10b90d88 ("powerpc/8xx: fix handling of early NULL pointer
dereference") moved the loading of r6 earlier in the code. As some
functions are called inbetween, r6 needs to be loaded again with the
address of swapper_pg_dir in order to set PTE pointers for
the Abatron BDI.

Fixes: 8c8c10b90d88 ("powerpc/8xx: fix handling of early NULL pointer dereference")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/powerpc/kernel/head_8xx.S

@@ -919,11 +919,12 @@ start_here:
 
 	/* set up the PTE pointers for the Abatron bdiGDB.
 	*/
-	tovirt(r6,r6)
 	lis	r5, abatron_pteptrs@h
 	ori	r5, r5, abatron_pteptrs@l
 	stw	r5, 0xf0(0)	/* Must match your Abatron config file */
 	tophys(r5,r5)
+	lis	r6, swapper_pg_dir@h
+	ori	r6, r6, swapper_pg_dir@l
 	stw	r6, 0(r5)
 
 /* Now turn on the MMU for real! */