linux/bitfield.h: replace __auto_type with auto

Replace "__auto_type" as described in commit:

2fb6915 compiler_types.h: add "auto" as a macro for "__auto_type"

[Yury: keep inclusions alphabetically ordered]

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> (reviewer:BITMAP API)
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>

Author: H. Peter Anvin

include/linux/bitfield.h

@@ -8,6 +8,7 @@
 #define _LINUX_BITFIELD_H
 
 #include <linux/build_bug.h>
+#include <linux/compiler.h>
 #include <linux/typecheck.h>
 #include <asm/byteorder.h>
 
@@ -243,7 +244,7 @@ __MAKE_OP(64)
 
 #define __field_prep(mask, val)						\
 	({								\
-		__auto_type __mask = (mask);				\
+		auto __mask = (mask);					\
 		typeof(__mask) __val = (val);				\
 		unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ?	\
 				       __ffs(__mask) : __ffs64(__mask);	\
@@ -252,7 +253,7 @@ __MAKE_OP(64)
 
 #define __field_get(mask, reg)						\
 	({								\
-		__auto_type __mask = (mask);				\
+		auto __mask = (mask);					\
 		typeof(__mask) __reg =  (reg);				\
 		unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ?	\
 				       __ffs(__mask) : __ffs64(__mask);	\