stm32: morse timer: standardize example

Simplify, clarify and synchronize the two morse LED blinker examples.
Prepare for one day extracting the core as common morse example code.

examples/stm32/f1/stm32-h103/timer/README.md

@@ -0,0 +1,15 @@
+# README
+
+This example demonstrates the use of timers to trigger an interrupt. This
+example will toggle a LED spelling out the following morse code:
+
+SOS -> ...---...
+
+using international morse timing, with a dot element of 100ms
+
+It's intended for the olimex stm32-h103 eval board. It should blink
+a LED on the board.
+
+## Board connections
+
+*none required*