[POWERPC] Reworking machine check handling and Fix 440/440A

This adds a cputable function pointer for the CPU-side machine
check handling. The semantic is still the same as the old one,
the one in ppc_md. overrides the one in cputable, though
ultimately we'll want to change that so the CPU gets first.

This removes CONFIG_440A which was a problem for multiplatform
kernels and instead fixes up the IVOR at runtime from a setup_cpu
function. The "A" version of the machine check also tweaks the
regs->trap value to differenciate the 2 versions at the C level.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/kernel/head_44x.S

@@ -289,11 +289,8 @@ interrupt_base:
 	CRITICAL_EXCEPTION(0x0100, CriticalInput, unknown_exception)
 
 	/* Machine Check Interrupt */
-#ifdef CONFIG_440A
-	MCHECK_EXCEPTION(0x0200, MachineCheck, machine_check_exception)
-#else
 	CRITICAL_EXCEPTION(0x0200, MachineCheck, machine_check_exception)
-#endif
+	MCHECK_EXCEPTION(0x0210, MachineCheckA, machine_check_exception)
 
 	/* Data Storage Interrupt */
 	START_EXCEPTION(DataStorage)
@@ -673,6 +670,15 @@ finish_tlb_load:
  * Global functions
  */
 
+/*
+ * Adjust the machine check IVOR on 440A cores
+ */
+_GLOBAL(__fixup_440A_mcheck)
+	li	r3,MachineCheckA@l
+	mtspr	SPRN_IVOR1,r3
+	sync
+	blr
+
 /*
  * extern void giveup_altivec(struct task_struct *prev)
  *