LogicalDisplayMappaer: allow external display to be default

deviceInfo already contains knowledge of whether the display should be
considered for the default display. LogicalDisplayMapper ignored this
information and stipulated that only internal displays can be default.

In the case of only external displays available, the first external
display should be considered the default to avoid boot failure as it
times out waiting for default display.

Use the deviceInfo provided flags to indicate default capability.

[bero@baylibre.com: Port to current AOSP]

Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
Signed-off-by: Bernhard Rosenkränzer <bero@baylibre.com>
Change-Id: I53947404fd491313b52f019806bac05499338e09