px4esc-v1 bootloader Update for upstream NuttX up_timer_initialize changes

up_timer_initialize became arm_timer_initialize

nuttx-configs/px4esc-v1/src/ostubs.c

@@ -150,7 +150,7 @@ void os_start(void)
   /* Initialize the OS's timer subsystem */
 #if !defined(CONFIG_SUPPRESS_INTERRUPTS) && !defined(CONFIG_SUPPRESS_TIMER_INTS) && \
     !defined(CONFIG_SYSTEMTICK_EXTCLK)
-  up_timer_initialize();
+  arm_timer_initialize();
 #endif
 
   /* Keep the compiler happy for a no return function */