locking/qspinlock: Fix build for anonymous union in older GCC compilers

One of my tests compiles the kernel with gcc 4.5.3, and I hit the
following build error:

  include/linux/semaphore.h: In function 'sema_init':
  include/linux/semaphore.h:35:17: error: unknown field 'val' specified in initializer
  include/linux/semaphore.h:35:17: warning: missing braces around initializer
  include/linux/semaphore.h:35:17: warning: (near initialization for '(anonymous).raw_lock.<anonymous>.val')

I bisected it down to:

 625e88b ("locking/qspinlock: Merge 'struct __qspinlock' into 'struct qspinlock'")

... which makes qspinlock have an anonymous union, which makes initializing it special
for older compilers. By adding strategic brackets, it makes the build
happy again.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Fixes: 625e88b ("locking/qspinlock: Merge 'struct __qspinlock' into 'struct qspinlock'")
Link: http://lkml.kernel.org/r/20180621203526.172ab5c4@vmware.local.home
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/asm-generic/qspinlock_types.h

@@ -63,7 +63,7 @@ typedef struct qspinlock {
 /*
  * Initializier
  */
-#define	__ARCH_SPIN_LOCK_UNLOCKED	{ .val = ATOMIC_INIT(0) }
+#define	__ARCH_SPIN_LOCK_UNLOCKED	{ { .val = ATOMIC_INIT(0) } }
 
 /*
  * Bitfields in the atomic value: