stm32f4: Add initial support for STM32F446 chip

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

src/stm32f4/internal.h

@@ -0,0 +1,21 @@
+#ifndef __STM32F4_INTERNAL_H
+#define __STM32F4_INTERNAL_H
+// Local definitions for STM32F4 code
+
+#include "stm32f4xx.h"
+
+#define GPIO(PORT, NUM) (((PORT)-'A') * 16 + (NUM))
+#define GPIO2PORT(PIN) ((PIN) / 16)
+#define GPIO2BIT(PIN) (1<<((PIN) % 16))
+
+#define GPIO_INPUT 0
+#define GPIO_OUTPUT 1
+#define GPIO_FUNCTION 2
+#define GPIO_ANALOG 3
+
+void enable_pclock(uint32_t periph_base);
+uint32_t get_pclock_frequency(uint32_t periph_base);
+void clock_setup(void);
+void gpio_peripheral(uint32_t gpio, uint32_t mode, uint32_t func, int pullup);
+
+#endif // internal.h