arm: refactor clearing of exception faults to common code

A number of SoCs clear out the Mem/Bus/Usage and Hard Fault exceptions
during init.  Lets refactor that into a common function so we don't have
to keep duplicating it over and over.

Change-Id: Ida908a9092db37447abcf3c9872f36937982f729
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

arch/arm/soc/st_stm32/stm32l4/soc.c

@@ -15,6 +15,7 @@
 #include <init.h>
 #include <soc.h>
 #include <arch/cpu.h>
+#include <cortex_m/exc.h>
 
 /**
  * @brief Perform basic hardware initialization at boot.
@@ -32,12 +33,7 @@ static int stm32l4_init(struct device *arg)
 
 	key = irq_lock();
 
-	/* Clear all faults */
-	_ScbMemFaultAllFaultsReset();
-	_ScbBusFaultAllFaultsReset();
-	_ScbUsageFaultAllFaultsReset();
-
-	_ScbHardFaultAllFaultsReset();
+	_ClearFaults();
 
 	/* Install default handler that simply resets the CPU
 	 * if configured in the kernel, NOP otherwise