Bluetooth: drivers: ipm_st32wb: Fix compilation

Issue faced while running bluetooth sample (peripheral, central, ...)

on stm32wb55rg with the latest zephyr version

Signed-off-by: Roger N'Guessan <roger.nguessan@st.com>
diff --git a/drivers/bluetooth/hci/ipm_stm32wb.c b/drivers/bluetooth/hci/ipm_stm32wb.c
index 029ac5a..38a0515 100644
--- a/drivers/bluetooth/hci/ipm_stm32wb.c
+++ b/drivers/bluetooth/hci/ipm_stm32wb.c
@@ -115,7 +115,7 @@
 			       hcievt->evtserial.evt.evtcode);
 			goto out;
 		default:
-			buf = bt_buf_get_evt(evtserial.evt.evtcode, false,
+			buf = bt_buf_get_evt(hcievt->evtserial.evt.evtcode, false,
 					     K_FOREVER);
 			break;
 		}