avr32: fix asm operand constraint in cmpxchg()

If the 'old' operand to cmpxchg() is a constant wider than 21 bits,
linking fails with a "relocation truncated to fit: R_AVR32_21S" error.

Fix this by replacing the "i" constraint with "Ks21" which makes the
compiler use a temporary register for out of range constants.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Acked-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Tested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Tested-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>

arch/avr32/include/asm/cmpxchg.h

@@ -57,7 +57,7 @@ static inline unsigned long __cmpxchg_u32(volatile int *m, unsigned long old,
 		"	brne	1b\n"
 		"2:\n"
 		: [ret] "=&r"(ret), [m] "=m"(*m)
-		: "m"(m), [old] "ir"(old), [new] "r"(new)
+		: "m"(m), [old] "Ks21r"(old), [new] "r"(new)
 		: "memory", "cc");
 	return ret;
 }