Move PIT timer init after CPU clock set

fixes #394

teensy4/startup.c

 	IOMUXC_GPR_GPR29 = 0xFFFFFFFF;
 #endif
 
-	// Undo PIT timer usage by ROM startup
-	CCM_CCGR1 |= CCM_CCGR1_PIT(CCM_CCGR_ON);
-	PIT_MCR = 0;
-	PIT_TCTRL0 = 0;
-	PIT_TCTRL1 = 0;
-	PIT_TCTRL2 = 0;
-	PIT_TCTRL3 = 0;
-
 	// must enable PRINT_DEBUG_STUFF in debug/print.h
 	printf_debug_init();
 	printf("\n***********IMXRT Startup**********\n");
 
 	asm volatile("nop\n nop\n nop\n nop": : :"memory"); // why oh why?
 
+	// Undo PIT timer usage by ROM startup
+	CCM_CCGR1 |= CCM_CCGR1_PIT(CCM_CCGR_ON);
+	PIT_MCR = 0;
+	PIT_TCTRL0 = 0;
+	PIT_TCTRL1 = 0;
+	PIT_TCTRL2 = 0;
+	PIT_TCTRL3 = 0;
+
 	// initialize RTC
 	if (!(SNVS_LPCR & SNVS_LPCR_SRTC_ENV)) {
 		// if SRTC isn't running, start it with default Jan 1, 2019