asm-generic: percpu: avoid Wshadow warning

Nesting macros that use the same local variable names causes
warnings when building with "make W=2":

include/asm-generic/percpu.h:117:14: warning: declaration of '__ret' shadows a previous local [-Wshadow]
include/asm-generic/percpu.h:126:14: warning: declaration of '__ret' shadows a previous local [-Wshadow]

These are fairly harmless, but since the warning comes from
a global header, the warning happens every time the headers
are included, which is fairly annoying.

Rename the variables to avoid shadowing and shut up the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/asm-generic/percpu.h

@@ -114,21 +114,21 @@ do {									\
 
 #define __this_cpu_generic_read_nopreempt(pcp)				\
 ({									\
-	typeof(pcp) __ret;						\
+	typeof(pcp) ___ret;						\
 	preempt_disable_notrace();					\
-	__ret = READ_ONCE(*raw_cpu_ptr(&(pcp)));			\
+	___ret = READ_ONCE(*raw_cpu_ptr(&(pcp)));			\
 	preempt_enable_notrace();					\
-	__ret;								\
+	___ret;								\
 })
 
 #define __this_cpu_generic_read_noirq(pcp)				\
 ({									\
-	typeof(pcp) __ret;						\
-	unsigned long __flags;						\
-	raw_local_irq_save(__flags);					\
-	__ret = raw_cpu_generic_read(pcp);				\
-	raw_local_irq_restore(__flags);					\
-	__ret;								\
+	typeof(pcp) ___ret;						\
+	unsigned long ___flags;						\
+	raw_local_irq_save(___flags);					\
+	___ret = raw_cpu_generic_read(pcp);				\
+	raw_local_irq_restore(___flags);				\
+	___ret;								\
 })
 
 #define this_cpu_generic_read(pcp)					\