Revert "sys_clock: start the microkernel ticker in the MICROKERNEL init level"

This reverts commit 3c66686a43.

That commit fixed announcing ticks before the microkernel was up, but
prevented devices initializing before the MICROKERNEL level from having
access to the hi-res part of the system clock, which they could not poll
anymore.

Change-Id: Ia1c55d482e63d295160942f97ebc8e8afd1e8315
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>

drivers/timer/sys_clock_init.c

@@ -32,10 +32,4 @@
 #include <init.h>
 #include <drivers/system_timer.h>
 
-SYS_INIT(_sys_clock_driver_init,
-#ifdef CONFIG_MICROKERNEL
-	MICROKERNEL,
-#else
-	NANOKERNEL,
-#endif
-	CONFIG_SYSTEM_CLOCK_INIT_PRIORITY);
+SYS_INIT(_sys_clock_driver_init, NANOKERNEL, CONFIG_SYSTEM_CLOCK_INIT_PRIORITY);