powerpc: Add plain English description for alignment exception oopses

If we take an alignment exception which we cannot fix, the oops
currently prints:

Unable to handle kernel paging request for unknown fault

Lets print something more useful:

Unable to handle kernel paging request for unaligned access at address 0xc0000000f77bba8f
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/fault.c

@@ -529,6 +529,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 		printk(KERN_ALERT "Unable to handle kernel paging request for "
 			"instruction fetch\n");
 		break;
+	case 0x600:
+		printk(KERN_ALERT "Unable to handle kernel paging request for "
+			"unaligned access at address 0x%08lx\n", regs->dar);
+		break;
 	default:
 		printk(KERN_ALERT "Unable to handle kernel paging request for "
 			"unknown fault\n");