tile: work around bug in the generic sys_llseek

sys_llseek should specify the high and low 32-bit seek values as "unsigned
int" but instead it specifies "unsigned long".  Since compat syscall
arguments are always sign-extended on tile, this means that a seek value
of 0xffffffff will be incorrectly interpreted as a value of -1ULL.

To avoid the risk of breaking binary compatibility on architectures
that already use sys_llseek this way, we follow the same path as MIPS
and provide a wrapper override.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: stable@kernel.org [v3.6 onwards]

arch/tile/include/asm/compat.h

@@ -288,6 +288,9 @@ long compat_sys_sync_file_range2(int fd, unsigned int flags,
 long compat_sys_fallocate(int fd, int mode,
 			  u32 offset_lo, u32 offset_hi,
 			  u32 len_lo, u32 len_hi);
+long compat_sys_llseek(unsigned int fd, unsigned int offset_high,
+		       unsigned int offset_low, loff_t __user * result,
+		       unsigned int origin);
 
 /* Assembly trampoline to avoid clobbering r0. */
 long _compat_sys_rt_sigreturn(void);