HAL_ChibiOS: removed wait on CAN peripheral in H7

these wait busy loops can take a very long time, and end up causing
interrupts to be lost elsewhere in the system, causing lost bytes on
UARTs

We should not have while loops waiting on peripharals like this. If we
do need to wait for a flag to clear then it needs to be done in a low
priority thread, or we need to check for completion in a timer

CAN still seems to work with this change, but needs flight testing

libraries/AP_HAL_ChibiOS/CANFDIface.cpp

@@ -721,8 +721,6 @@ void CanIface::pollErrorFlagsFromISR()
             if (((1 << pending_tx_[i].index) & can_->TXBRP)) {
                 can_->TXBCR = 1 << pending_tx_[i].index;  // Goodnight sweet transmission
                 error_cnt_++;
-                //Wait for Cancelation to finish
-                while (!(can_->TXBCF & (1 << pending_tx_[i].index))) {}
                 served_aborts_cnt_++;
             }
         }
@@ -736,8 +734,6 @@ void CanIface::discardTimedOutTxMailboxes(uavcan::MonotonicTime current_time)
         if (((1 << pending_tx_[i].index) & can_->TXBRP) && pending_tx_[i].deadline < current_time) {
             can_->TXBCR = 1 << pending_tx_[i].index;  // Goodnight sweet transmission
             error_cnt_++;
-            //Wait for Cancelation to finish
-            while (!(can_->TXBCF & (1 << pending_tx_[i].index))) {}
         }
     }
 }