sparc64: Improvde documentation and readability of atomic backoff code.

Document what's going on in asm/backoff.h with a large and descriptive
comment.  Refer to it above the cpu_relax() definition in
asm/processor_64.h

Rename the pause patching section to have "3insn" in it's name like
the other patching sections do.

Based upon feedback from Sam Ravnborg.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/kernel/setup_64.c b/arch/sparc/kernel/setup_64.c
index b45cff4..0eaf005 100644
--- a/arch/sparc/kernel/setup_64.c
+++ b/arch/sparc/kernel/setup_64.c
@@ -320,8 +320,8 @@
 {
 	struct pause_patch_entry *p;
 
-	p = &__pause_patch;
-	while (p < &__pause_patch_end) {
+	p = &__pause_3insn_patch;
+	while (p < &__pause_3insn_patch_end) {
 		unsigned long i, addr = p->addr;
 
 		for (i = 0; i < 3; i++) {