Bluetooth: hci_core: Fix build warnings

This fixes the following warnings:

net/bluetooth/hci_core.c: In function ‘hci_register_dev’:
net/bluetooth/hci_core.c:2620:54: warning: ‘%d’ directive output may
be truncated writing between 1 and 10 bytes into a region of size 5
[-Wformat-truncation=]
 2620 |         snprintf(hdev->name, sizeof(hdev->name), "hci%d", id);
      |                                                      ^~
net/bluetooth/hci_core.c:2620:50: note: directive argument in the range
[0, 2147483647]
 2620 |         snprintf(hdev->name, sizeof(hdev->name), "hci%d", id);
      |                                                  ^~~~~~~
net/bluetooth/hci_core.c:2620:9: note: ‘snprintf’ output between 5 and
14 bytes into a destination of size 8
 2620 |         snprintf(hdev->name, sizeof(hdev->name), "hci%d", id);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>