Revert accessing CAN device with a map indexing on dev name

Revert accessing CAN device with a map indexing on dev name

Main reason for that behavior revert is because of generator that rely
on CAN device name and so we have point on these object by specify the
device name.

Instead of shared pointer between objects, instead binding is based on
device name. With a device name you can get the shared pointer on it using
new static method from can_bus_t object.

Change-Id: I331e0ad8d03c88a15c697d12a9fce3699b0cd962
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>