powerpc/44x: Fix/Initialize PID to kernel PID before the TLB search

Initialize the PID register with kernel pid (0) before we start
setting the TLB mapping for KEXEC. Also set the MMUCR[TID] to kernel
PID.

This was spotted while testing the kexec on ISS for 47x. ISS  doesn't
return a successful tlbsx for a kernel address with PID set to a user PID.
Though the hardware/qemu/simics work fine.

This patch is harmless and initializes the PID to 0 (kernel PID) which
is usually the case during a normal kernel boot. This would fix the kexec
on ISS for 440. I have tested this patch on sequoia board.
Signed-off-by: Suzuki K Poulose <suzuki@in.ibm.com>
Cc: Josh Boyer <jwboyer@gmail.com>
Signed-off-by: Josh Boyer <jwboyer@gmail.com>

arch/powerpc/kernel/misc_32.S

@@ -761,8 +761,12 @@ relocate_new_kernel:
 	mr	r30, r4
 	mr	r31, r5
 
-	/* Load our MSR_IS and TID to MMUCR for TLB search */
-	mfspr	r3,SPRN_PID
+	/* 
+	 * Load the PID with kernel PID (0).
+	 * Also load our MSR_IS and TID to MMUCR for TLB search.
+	 */
+	li	r3, 0
+	mtspr	SPRN_PID, r3
 	mfmsr	r4
 	andi.	r4,r4,MSR_IS@l
 	beq	wmmucr