[PATCH] fix oops on resume from apm bios initiated suspend

From: Milton Miller <miltonm@bga.com>

mm is NULL for kernel threads without their own context.  active_mm is
maintained the one we lazly switch from.

Without this patch, apm bios initiated suspend events (eg panel close)
cause an oops on resume in the LDT restore, killing kapmd, which causes
further events to not be polled.

arch/i386/kernel/suspend.c

@@ -114,7 +114,7 @@ static void fix_processor_context(void)
         cpu_gdt_table[cpu][GDT_ENTRY_TSS].b &= 0xfffffdff;
 
 	load_TR_desc();				/* This does ltr */
-	load_LDT(&current->mm->context);	/* This does lldt */
+	load_LDT(&current->active_mm->context);	/* This does lldt */
 
 	/*
 	 * Now maybe reload the debug registers