lib: It is no longer necessary to modify the stm32f1 code

Now that the stm32f1 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

@@ -46,8 +46,7 @@ version 1.9.0 (extracted 20190116).
 
 The stm32f1 directory contains code from STMicroelectronics:
   http://www.st.com/en/embedded-software/stm32cubef1.html
-version 1.8.0 (extracted 20190721). It has been modified to compile
-with gcc's LTO feature. See stm32f1.patch for the modifications.
+version 1.8.0 (extracted 20190721).
 
 The stm32f4 directory contains code from STMicroelectronics:
   http://www.st.com/en/embedded-software/stm32cubef4.html

lib/stm32f1/stm32f1.patch

@@ -1,13 +0,0 @@
-diff --git a/lib/stm32f1/system_stm32f1xx.c b/lib/stm32f1/system_stm32f1xx.c
-index be2da1b1..fb6c279c 100644
---- a/lib/stm32f1/system_stm32f1xx.c
-+++ b/lib/stm32f1/system_stm32f1xx.c
-@@ -154,7 +154,7 @@ const uint8_t APBPrescTable[8U] =  {0, 0, 0, 0, 1, 2, 3, 4};
-   * @param  None
-   * @retval None
-   */
--void SystemInit (void)
-+void __attribute__((externally_visible)) SystemInit (void)
- {
-   /* Reset the RCC clock configuration to the default reset state(for debug purpose) */
-   /* Set HSION bit */

lib/stm32f1/system_stm32f1xx.c

@@ -154,7 +154,7 @@ const uint8_t APBPrescTable[8U] =  {0, 0, 0, 0, 1, 2, 3, 4};
   * @param  None
   * @retval None
   */
-void __attribute__((externally_visible)) SystemInit (void)
+void SystemInit (void)
 {
   /* Reset the RCC clock configuration to the default reset state(for debug purpose) */
   /* Set HSION bit */