src/timer.rs: disable creation of TIM4 for stm32l4+ because of PAC error.

In the current release of the stm32l4 PAC,
the `cnt` register of TIM3 and tim4 have an incorrect width.
This was fixed in stm32-rs#669, once this is included in the next
release, we will be able to start using TIM3 and TIM4.

Author: jspngh

src/timer.rs

@@ -317,8 +317,8 @@ hal! {
     // feature = "stm32l4s5",
     // feature = "stm32l4r7",
     // feature = "stm32l4s7",
-    feature = "stm32l4r9",
-    feature = "stm32l4s9",
+    // feature = "stm32l4r9",
+    // feature = "stm32l4s9",
 ))]
 hal! {
     TIM4:  (tim4, free_running_tim4, APB1R1, u16),