arm/arm_assert.c Fix dumping of status from ISR

The status dump did not work if the first fault triggers before
the first context switch (during nx_start()).

arch/arm/src/common/arm_assert.c

@@ -366,8 +366,7 @@ static void arm_dumpstate(void)
 
   if (CURRENT_REGS)
     {
-      memcpy(rtcb->xcp.regs,
-             (uintptr_t *)CURRENT_REGS, XCPTCONTEXT_SIZE);
+      rtcb->xcp.regs = (uint32_t *)CURRENT_REGS;
     }
   else
     {