MIPS: ptrace.h: Add a missing include

Commit a79ebea62010 (MIPS: ptrace: Fix user pt_regs definition,
use in ptrace_{get, set}regs()) converted struct pt_regs to use __u64.
Some userspace applications (e.g. GDB) include this file directly,
and fail to see this type. Fix by including <linux/types.h>.

The patch fixes the following build failure with GDB 7.8 when using
GLIBC headers created against Linux 3.17:

In file included from /home/aaro/los/work/shared/gdb-7.8/gdb/mips-linux-nat.c:37:0:
/home/aaro/los/work/mips/rootfs/mips-linux-gnu/usr/include/asm/ptrace.h:32:2: error: unknown type name '__u64'
__u64 regs[32];
^
/home/aaro/los/work/mips/rootfs/mips-linux-gnu/usr/include/asm/ptrace.h:35:2: error: unknown type name '__u64'
__u64 lo;
^
/home/aaro/los/work/mips/rootfs/mips-linux-gnu/usr/include/asm/ptrace.h:36:2: error: unknown type name '__u64'
__u64 hi;
^

Fixes: a79ebea62010 ("MIPS: ptrace: Fix user pt_regs definition, use in ptrace_{get, set}regs()")
Cc: [e-mail] # 3.17
Signed-off-by: Aaro Koskinen <[e-mail]>
Cc: Alex Smith <[e-mail]>
Cc: [e-mail]
Patchwork: https://patchwork.linux-mips.org/patch/8067/
Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/include/uapi/asm/ptrace.h

···
 #ifndef _UAPI_ASM_PTRACE_H
 #define _UAPI_ASM_PTRACE_H
 
+#include <linux/types.h>
+
 /* 0 - 31 are integer registers, 32 - 63 are fp registers.  */
 #define FPR_BASE	32
 #define PC		64