armcm_timer: Unify udelay() implementation

Move the udelay() code from various arm board directories into the
src/generic/armcm_timer.c code.

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

src/stm32f1/internal.h

@@ -10,6 +10,4 @@
 extern GPIO_TypeDef *const digital_regs[];
 extern uint32_t const digital_pins[];
 
-void udelay(uint32_t usecs);
-
 #endif // internal.h

src/stm32f1/main.c

@@ -131,20 +131,6 @@ void io_config(void)
     LL_DBGMCU_SetTracePinAssignment(LL_DBGMCU_TRACE_NONE);
 }
 
-// Implement simple early-boot delay mechanism
-void
-udelay(uint32_t usecs)
-{
-    if (!(CoreDebug->DEMCR & CoreDebug_DEMCR_TRCENA_Msk)) {
-        CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
-        DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
-    }
-
-    uint32_t end = timer_read_time() + timer_from_us(usecs);
-    while (timer_is_before(timer_read_time(), end))
-        ;
-}
-
 // Main entry point
 int
 main(void)

src/stm32f1/usbserial.c

@@ -6,6 +6,7 @@
 
 #include <string.h> // NULL
 #include "autoconf.h" // CONFIG_STM_FLASH_START_2000
+#include "board/armcm_timer.h" // udelay
 #include "board/gpio.h" // gpio_out_setup
 #include "board/io.h" // writeb
 #include "board/irq.h" // irq_disable