Bluetooth: Fix the LE Read Connection Interval response layout

The response to HCI_OP_LE_READ_CONN_INTERVAL carries a
Minimum_Supported_Connection_Interval octet between the status and
Num_Groups, which was missing from the structure. Without it the minimum
interval was read as the number of groups, and every group after it
from one octet off.

Take the minimum interval used to clamp the default rate parameters from
that field rather than the smallest group minimum, as the number of
groups can be zero, which left it unset.

Fixes: 2f8784cfe8a9 ("Bluetooth: Add support for Shorter Connection Interval (SCI) feature")
Assisted-by: OpenCode:claude-opus-5.5
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>