stmhal/diskio: Add provision for default returns for ioctl INIT/SEC_SIZE.

If None was returned for such requests (which likely means that user simply
didn't handle them), it means successful init and default sector size of 512
bytes respectively. This makes only BP_IOCTL_SEC_COUNT a mandatory request,
and thus re-establishes parity with old interface, where only .count() is
mandatory().

stmhal/diskio.c

@@ -63,7 +63,7 @@ DSTATUS disk_initialize (
         vfs->u.ioctl[2] = MP_OBJ_NEW_SMALL_INT(BP_IOCTL_INIT);
         vfs->u.ioctl[3] = MP_OBJ_NEW_SMALL_INT(0); // unused
         mp_obj_t ret = mp_call_method_n_kw(2, 0, vfs->u.ioctl);
-        if (MP_OBJ_SMALL_INT_VALUE(ret) != 0) {
+        if (ret != mp_const_none && MP_OBJ_SMALL_INT_VALUE(ret) != 0) {
             // error initialising
             return STA_NOINIT;
         }
@@ -203,7 +203,12 @@ DRESULT disk_ioctl (
                 vfs->u.ioctl[2] = MP_OBJ_NEW_SMALL_INT(BP_IOCTL_SEC_SIZE);
                 vfs->u.ioctl[3] = MP_OBJ_NEW_SMALL_INT(0); // unused
                 mp_obj_t ret = mp_call_method_n_kw(2, 0, vfs->u.ioctl);
-                *((WORD*)buff) = mp_obj_get_int(ret);
+                if (ret == mp_const_none) {
+                    // Default sector size
+                    *((WORD*)buff) = 512;
+                } else {
+                    *((WORD*)buff) = mp_obj_get_int(ret);
+                }
                 return RES_OK;
             }