fix pointer casting warning

fixes following warning:
libboard/common/source/board_cstartup_gnu.c:137:11: warning: assignment to 'void (*)(void)' from 'unsigned int' makes pointer from integer without a cast [-Wint-conversion]
  appReset = pSrc[1];
diff --git a/firmware/libboard/common/source/board_cstartup_gnu.c b/firmware/libboard/common/source/board_cstartup_gnu.c
index 775f325..f2d17af 100644
--- a/firmware/libboard/common/source/board_cstartup_gnu.c
+++ b/firmware/libboard/common/source/board_cstartup_gnu.c
@@ -134,7 +134,7 @@
 

 	pSrc = (unsigned int *) ((unsigned char *)IFLASH_ADDR + BOARD_DFU_BOOT_SIZE);

 	SCB->VTOR = ((unsigned int)(pSrc)) | (0x0 << 7);

-	appReset = pSrc[1];

+	appReset = (void(*)(void))pSrc[1];

 

 	g_dfu->state = DFU_STATE_appIDLE;