Generic semaphore implementation

Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility.  Thanks to Peter Zijlstra for fixing the lockdep
warning.  Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>

arch/um/sys-i386/ksyms.c

@@ -1,17 +1,5 @@
 #include "linux/module.h"
-#include "linux/in6.h"
-#include "linux/rwsem.h"
-#include "asm/byteorder.h"
-#include "asm/delay.h"
-#include "asm/semaphore.h"
-#include "asm/uaccess.h"
 #include "asm/checksum.h"
-#include "asm/errno.h"
-
-EXPORT_SYMBOL(__down_failed);
-EXPORT_SYMBOL(__down_failed_interruptible);
-EXPORT_SYMBOL(__down_failed_trylock);
-EXPORT_SYMBOL(__up_wakeup);
 
 /* Networking helper routines. */
 EXPORT_SYMBOL(csum_partial);