Bluetooth: Add 'eir_len' param to mgmt_device_found()

This patch adds a new parameter to mgmt_device_found() to inform
the length of 'eir' pointer.

EIR data from LE advertising report event doesn't have a fixed length
as EIR data from extended inquiry result event does. We needed to
change mgmt_device_found() so it copies 'eir_len' bytes instead of
HCI_MAX_EIR_LENGTH.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>