seqlock: avoid -Wshadow warnings

When building with W=2, there is a flood of warnings about the seqlock
macros shadowing local variables:

  19806 linux/seqlock.h:331:11: warning: declaration of 'seq' shadows a previous local [-Wshadow]
     48 linux/seqlock.h:348:11: warning: declaration of 'seq' shadows a previous local [-Wshadow]
      8 linux/seqlock.h:379:11: warning: declaration of 'seq' shadows a previous local [-Wshadow]

Prefix the local variables to make the warning useful elsewhere again.

Fixes: 52ac39e5 ("seqlock: seqcount_t: Implement all read APIs as statement expressions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201026165044.3722931-1-arnd@kernel.org

include/linux/seqlock.h

@@ -328,13 +328,13 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  */
 #define __read_seqcount_begin(s)					\
 ({									\
-	unsigned seq;							\
+	unsigned __seq;							\
 									\
-	while ((seq = __seqcount_sequence(s)) & 1)			\
+	while ((__seq = __seqcount_sequence(s)) & 1)			\
 		cpu_relax();						\
 									\
 	kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);			\
-	seq;								\
+	__seq;								\
 })
 
 /**
@@ -345,10 +345,10 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  */
 #define raw_read_seqcount_begin(s)					\
 ({									\
-	unsigned seq = __read_seqcount_begin(s);			\
+	unsigned _seq = __read_seqcount_begin(s);			\
 									\
 	smp_rmb();							\
-	seq;								\
+	_seq;								\
 })
 
 /**
@@ -376,11 +376,11 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  */
 #define raw_read_seqcount(s)						\
 ({									\
-	unsigned seq = __seqcount_sequence(s);				\
+	unsigned __seq = __seqcount_sequence(s);			\
 									\
 	smp_rmb();							\
 	kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);			\
-	seq;								\
+	__seq;								\
 })
 
 /**