lib: It is no longer necessary to modify the stm32f4 code

Now that the stm32f4 code uses the armcm_boot mechanism, it is no
longer necessary for SystemInit to be externally visible.

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

lib/README

@@ -51,8 +51,7 @@ with gcc's LTO feature. See stm32f1.patch for the modifications.
 
 The stm32f4 directory contains code from STMicroelectronics:
   http://www.st.com/en/embedded-software/stm32cubef4.html
-version 1.24.0 (extracted 20190723). It has been modified to compile
-with gcc's LTO feature. See stm32f4.patch for the modifications.
+version 1.24.0 (extracted 20190723).
 
 The hub-ctrl directory contains code from:
   https://github.com/codazoda/hub-ctrl.c/

lib/stm32f4/stm32f4.patch

@@ -1,13 +0,0 @@
-diff --git a/lib/stm32f4/system_stm32f4xx.c b/lib/stm32f4/system_stm32f4xx.c
-index 11c18d1a..b94cfb2f 100644
---- a/lib/stm32f4/system_stm32f4xx.c
-+++ b/lib/stm32f4/system_stm32f4xx.c
-@@ -163,7 +163,7 @@ const uint8_t APBPrescTable[8]  = {0, 0, 0, 0, 1, 2, 3, 4};
-   * @param  None
-   * @retval None
-   */
--void SystemInit(void)
-+void __attribute__((externally_visible)) SystemInit(void)
- {
-   /* FPU settings ------------------------------------------------------------*/
-   #if (__FPU_PRESENT == 1) && (__FPU_USED == 1)

lib/stm32f4/system_stm32f4xx.c

@@ -163,7 +163,7 @@ const uint8_t APBPrescTable[8]  = {0, 0, 0, 0, 1, 2, 3, 4};
   * @param  None
   * @retval None
   */
-void __attribute__((externally_visible)) SystemInit(void)
+void SystemInit(void)
 {
   /* FPU settings ------------------------------------------------------------*/
   #if (__FPU_PRESENT == 1) && (__FPU_USED == 1)