Bluetooth: eir: Move EIR/Adv Data functions to its own file

This moves functions manipulating EIR/Adv Data to its own file so it
can be reused by other files.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>