Portenta H7: configure LSE as BYPASS

Author: facchinm

targets/targets.json

@@ -2862,6 +2862,10 @@
                 "value": "25000000",
                 "macro_name": "HSE_VALUE"
             },
+            "lse_bypass": {
+                "help": "1 to use an oscillator (not a crystal) on 32k LSE",
+                "value": "1"
+            },
             "usb_speed": {
                 "help": "USE_USB_OTG_FS or USE_USB_OTG_HS or USE_USB_HS_IN_FS",
                 "value": "USE_USB_OTG_HS"