mimxrt: Improve ticks and sleep functions using GPT.

SysTick cannot wake the CPU from WFI/WFE so a hardware timer is needed to
keep track of ticks/delay (similar to the nrf port).

Fixes issue #7234.

Signed-off-by: Damien George <damien@micropython.org>

ports/mimxrt/board_init.c

@@ -53,9 +53,6 @@ void board_init(void) {
     // Enable IOCON clock
     CLOCK_EnableClock(kCLOCK_Iomuxc);
 
-    // 1ms tick timer
-    SysTick_Config(SystemCoreClock / 1000);
-
     // ------------- USB0 ------------- //
 
     // Clock
@@ -85,10 +82,6 @@ void board_init(void) {
     //  CLOCK_EnableUsbhs1Clock(kCLOCK_Usb480M, 480000000U);
 }
 
-void SysTick_Handler(void) {
-    systick_ms++;
-}
-
 void USB_OTG1_IRQHandler(void) {
     tud_int_handler(0);
     tud_task();