powerpc: Fix 32-bit SMP build

Commit 69e3cea8d5fd526 ("powerpc/smp: Make start_secondary_resume
available to all CPU variants") introduced start_secondary_resume to
misc_32.S, however it uses a 64-bit instruction which is not valid on
32-bit platforms.  Use 'stw' instead.

Reported-by: Richard Cochran <richardcochran@gmail.com>
Tested-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/kernel/misc_32.S

@@ -700,7 +700,7 @@ _GLOBAL(start_secondary_resume)
 	rlwinm	r1,r1,0,0,(31-THREAD_SHIFT)	/* current_thread_info() */
 	addi	r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD
 	li	r3,0
-	std	r3,0(r1)		/* Zero the stack frame pointer	*/
+	stw	r3,0(r1)		/* Zero the stack frame pointer	*/
 	bl	start_secondary
 	b	.
 #endif /* CONFIG_SMP */