Build: Minor IAR warnings elimination and fix for 8f17a711

Update the IAR CMSE_FLAG handling for 8f17a711

Fixed a few warnings about unused variables with IAR

Disabled some harmless warnings for IAR

Signed-off-by: TTornblom <thomas.tornblom@iar.com>
Change-Id: I7197ae009e3e85bcb8d8b21b7528108d966ee330
diff --git a/platform/ext/common/uart_stdout.c b/platform/ext/common/uart_stdout.c
index 075a2b7..811dfe4 100644
--- a/platform/ext/common/uart_stdout.c
+++ b/platform/ext/common/uart_stdout.c
@@ -96,6 +96,7 @@
     ret = STDIO_DRIVER.Control(ARM_USART_MODE_ASYNCHRONOUS,
                                DEFAULT_UART_BAUDRATE);
     ASSERT_HIGH(ret);
+    (void)ret;
 
     (void)STDIO_DRIVER.Control(ARM_USART_CONTROL_TX, 1);
 }
@@ -108,4 +109,5 @@
 
     ret = STDIO_DRIVER.Uninitialize();
     ASSERT_HIGH(ret);
+    (void)ret;
 }