MIPS: Fix comment.

The value is incorrect and were copied in Linux 2.5.4 from i386.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/thread_info.h

@@ -29,10 +29,11 @@ struct thread_info {
 	__u32			cpu;		/* current CPU */
 	int			preempt_count;	/* 0 => preemptable, <0 => BUG */
 
-	mm_segment_t		addr_limit;	/* thread address space:
-						   0-0xBFFFFFFF for user-thead
-						   0-0xFFFFFFFF for kernel-thread
-						*/
+	mm_segment_t		addr_limit;	/*
+						 * thread address space limit:
+						 * 0x7fffffff for user-thead
+						 * 0xffffffff for kernel-thread
+						 */
 	struct restart_block	restart_block;
 	struct pt_regs		*regs;
 };