[POWERPC] Initialize paca->current earlier

Currently, we initialize the "current" pointer in the PACA (which
is used by the "current" macro in the kernel) before calling
setup_system(). That means that early_setup() is called with
current still "NULL" which is -not- a good idea. It happens to
work so far but breaks with lockdep when early code calls printk.

This changes it so that all PACAs are statically initialized with
__current pointing to the init task. For non-0 CPUs, this is fixed
up before use.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/head_64.S

@@ -1521,10 +1521,6 @@ _INIT_GLOBAL(start_here_common)
 	li	r0,0
 	stdu	r0,-STACK_FRAME_OVERHEAD(r1)
 
-	/* ptr to current */
-	LOAD_REG_IMMEDIATE(r4, init_task)
-	std	r4,PACACURRENT(r13)
-
 	/* Load the TOC */
 	ld	r2,PACATOC(r13)
 	std	r1,PACAKSAVE(r13)

arch/powerpc/kernel/paca.c

@@ -73,6 +73,7 @@ struct slb_shadow slb_shadow[] __cacheline_aligned = {
 	.kernel_toc = (unsigned long)(&__toc_start) + 0x8000UL,		    \
 	.hw_cpu_id = 0xffff,						    \
 	.slb_shadow_ptr = &slb_shadow[number],				    \
+	.__current = &init_task,					    \
 }
 
 struct paca_struct paca[] = {