[stm32x] Use modern header include paths.

Replace includes of stm32/YY/xxxx.h with stm32/xxxx.h
Replace stm32/YY/nvic.h with cm3/nvic.h.
In some cases, the include list was resorted alphabetically when it was
complicated and I was reviewing them manually, but most of this was
automatically done.

examples/stm32/f2/jobygps/usart_printf/usart_printf.c

@@ -20,10 +20,10 @@
 
 #include <stdio.h>
 #include <errno.h>
-#include <libopencm3/stm32/f2/gpio.h>
+#include <libopencm3/stm32/gpio.h>
 #include <libopencm3/stm32/usart.h>
 #include <libopencm3/cm3/nvic.h>
-#include <libopencm3/stm32/f2/rcc.h>
+#include <libopencm3/stm32/rcc.h>
 
 int _write(int file, char *ptr, int len);