armcm_irq: Move ARM Cortex-M irq handling to new file

The irq handling in sam3x8e isn't specific to the sam3x8e proccessor -
it's generic for all armcm type machines.  So, move the definitions
into a new file generic/armcm-irq.c

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/sam3x8e/main.c

@@ -4,7 +4,7 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
-#include "board/misc.h" // console_get_input
+#include "board/misc.h" // alloc_maxsize
 #include "sam3x8e.h" // WDT
 #include "sched.h" // sched_main
 
@@ -29,34 +29,6 @@ watchdog_init(void)
 DECL_INIT(watchdog_init);
 
 
-/****************************************************************
- * irq clearing on fault
- ****************************************************************/
-
-// Clear the active irq if a shutdown happened in an irq handler
-static void
-clear_active_irq(void)
-{
-    uint32_t psr;
-    asm volatile("mrs %0, psr" : "=r" (psr));
-    if (!(psr & 0x1ff))
-        // Shutdown did not occur in an irq - nothing to do.
-        return;
-    // Clear active irq status
-    psr = 1<<24; // T-bit
-    uint32_t temp;
-    asm volatile(
-        "  push { %1 }\n"
-        "  adr %0, 1f\n"
-        "  push { %0 }\n"
-        "  push { r0, r1, r2, r3, r12, lr }\n"
-        "  bx %2\n"
-        "1:\n"
-        : "=&r"(temp) : "r"(psr), "r"(0xfffffff9) : "cc");
-}
-DECL_SHUTDOWN(clear_active_irq);
-
-
 /****************************************************************
  * misc functions
  ****************************************************************/