[LIB]: Consolidate _atomic_dec_and_lock()

Several implementations were essentialy a common piece of C code using
the cmpxchg() macro.  Put the implementation in one spot that everyone
can share, and convert sparc64 over to using this.

Alpha is the lone arch-specific implementation, which codes up a
special fast path for the common case in order to avoid GP reloading
which a pure C version would require.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/ppc/lib/Makefile b/arch/ppc/lib/Makefile
index f1e1fb4..50358e4 100644
--- a/arch/ppc/lib/Makefile
+++ b/arch/ppc/lib/Makefile
@@ -2,7 +2,7 @@
 # Makefile for ppc-specific library files..
 #
 
-obj-y			:= checksum.o string.o strcase.o dec_and_lock.o div64.o
+obj-y			:= checksum.o string.o strcase.o div64.o
 
 obj-$(CONFIG_8xx)	+= rheap.o
 obj-$(CONFIG_CPM2)	+= rheap.o