improve sys_newuname() for compat architectures

On an architecture that supports 32-bit compat we need to override the
reported machine in uname with the 32-bit value.  Instead of doing this
separately in every architecture introduce a COMPAT_UTS_MACHINE define in
<asm/compat.h> and apply it directly in sys_newuname().

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/s390/kernel/entry.h

@@ -24,7 +24,6 @@ int __cpuinit start_secondary(void *cpuvoid);
 void __init startup_init(void);
 void die(const char * str, struct pt_regs * regs, long err);
 
-struct new_utsname;
 struct s390_mmap_arg_struct;
 struct fadvise64_64_args;
 struct old_sigaction;
@@ -32,7 +31,6 @@ struct old_sigaction;
 long sys_mmap2(struct s390_mmap_arg_struct __user  *arg);
 long sys_s390_ipc(uint call, int first, unsigned long second,
 	     unsigned long third, void __user *ptr);
-long sys_s390_newuname(struct new_utsname __user *name);
 long sys_s390_personality(unsigned long personality);
 long sys_s390_fadvise64(int fd, u32 offset_high, u32 offset_low,
 		    size_t len, int advice);