MIPS: include: Mark __xchg as __always_inline

Commit ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING
forcibly") allows compiler to uninline functions marked as 'inline'.
In cace of __xchg this would cause to reference function
__xchg_called_with_bad_pointer, which is an error case
for catching bugs and will not happen for correct code, if
__xchg is inlined.

Signed-off-by: Thomas Bogendoerfer <[e-mail]>
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Signed-off-by: Paul Burton <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: James Hogan <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

arch/mips/include/asm/cmpxchg.h

···
 extern unsigned long __xchg_small(volatile void *ptr, unsigned long val,
 				  unsigned int size);
 
-static inline unsigned long __xchg(volatile void *ptr, unsigned long x,
-				   int size)
+static __always_inline
+unsigned long __xchg(volatile void *ptr, unsigned long x, int size)
 {
 	switch (size) {
 	case 1: