a-st-ext: mark examples as a note

Examples are usually in note blocks already.  Make these consistent.

The text about compare-and-swap example should probably be improved and
moved above the example.

Signed-off-by: Radim Krčmář <[email protected]>

src/a-st-ext.adoc

@@ -229,6 +229,8 @@ those with both bits clear, but may result in lower performance.
 
 <<<
 
+[NOTE]
+====
 [[cas]]
 [source,asm]
 .Sample code for compare-and-swap function using LR/SC.
@@ -250,6 +252,7 @@ those with both bits clear, but may result in lower performance.
 LR/SC can be used to construct lock-free data structures. An example
 using LR/SC to implement a compare-and-swap function is shown in
 <<cas>>. If inlined, compare-and-swap functionality need only take four instructions.
+====
 
 [[sec:lrscseq]]
 === Eventual Success of Store-Conditional Instructions
@@ -434,6 +437,8 @@ both imply additional unnecessary ordering as compared to AMOs with the
 corresponding _aq_ or _rl_ bit set.
 ====
 
+[NOTE]
+====
 An example code sequence for a critical section guarded by a
 test-and-test-and-set spinlock is shown in
 Example <<critical>>. Note the first AMO is marked _aq_ to
@@ -457,8 +462,6 @@ relinquishment.
         # ...
         amoswap.w.rl x0, x0, (a0) # Release lock by storing 0.
 
-[NOTE]
-====
 We recommend the use of the AMO Swap idiom shown above for both lock
 acquire and release to simplify the implementation of speculative lock
 elision. cite:[Rajwar:2001:SLE]