Merged in antmerlino/nuttx/stm32f7-hsebypclk (pull request #845)

arch/arc/stm32f7: Add support for using the HSE in bypass mode, configured by board.h

Approved-by: Gregory Nutt <gnutt@nuttx.org>

arch/arm/src/stm32f7/stm32f76xx77xx_rcc.c

@@ -723,6 +723,11 @@ static void stm32_stdclockconfig(void)
   /* Enable External High-Speed Clock (HSE) */
 
   regval  = getreg32(STM32_RCC_CR);
+#ifdef STM32_HSEBYP_ENABLE          /* May be defined in board.h header file */
+  regval |= RCC_CR_HSEBYP;          /* Enable HSE clock bypass */
+#else
+  regval &= ~RCC_CR_HSEBYP;         /* Disable HSE clock bypass */
+#endif
   regval |= RCC_CR_HSEON;           /* Enable HSE */
   putreg32(regval, STM32_RCC_CR);