locking/rwsem, x86: Drop a bogus cc clobber

With the addition of uses of GCC's condition code outputs in commit:

  35ccfb7114 ("x86, asm: Use CC_SET()/CC_OUT() in <asm/rwsem.h>")

... there's now an overlap of outputs and clobbers in __down_write_trylock().

Such overlaps are generally getting tagged with an error (occasionally
even with an ICE). I can't really tell why plain GCC 6.2 doesn't detect
this (judging by the code it is meant to), while the slightly modified
one I use does. Since condition code clobbers are never necessary on x86
(other than perhaps for documentation purposes, which doesn't really
get done consistently), remove it altogether rather than inventing
something like CC_CLOBBER (to accompany CC_SET/CC_OUT).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/57E003CC0200007800110102@prv-mh.provo.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/rwsem.h

@@ -154,7 +154,7 @@ static inline bool __down_write_trylock(struct rw_semaphore *sem)
 		     : "+m" (sem->count), "=&a" (tmp0), "=&r" (tmp1),
 		       CC_OUT(e) (result)
 		     : "er" (RWSEM_ACTIVE_WRITE_BIAS)
-		     : "memory", "cc");
+		     : "memory");
 	return result;
 }