MIPS: Fix a typo in watchpoint register structure.

This fixes the ptrace ABI for watch registers, and should allow 64bit
kernels to use the watch register support.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/ptrace.h

@@ -105,7 +105,7 @@ struct pt_watch_regs {
 	enum pt_watch_style style;
 	union {
 		struct mips32_watch_regs mips32;
-		struct mips32_watch_regs mips64;
+		struct mips64_watch_regs mips64;
 	};
 };