h/q/d: Consider dropped layers in load based MDP comp

While batching up layers for load based MDP composition, filter
out dropped layers.

CRs-Fixed: 607196

Change-Id: I78031f1094330e1d960ceb56d5441c27a041e48c
qdutils: Pre-allocate initial buffer for getline().

Some frameworks override malloc() and free() but not getline().
Pre-allocating the buffer avoids heap mismatch on free().

Change-Id: I9bd934f701ad7dbc10ec2aa21967e2a626c496f4
hwc/overlay: validate and prepare frame

Send the entire frame (array of overlays) to driver, so that it would
check pipes params and the whole frame wrt bandwidth and SMP.

Now, the overlay's commit API just prepares an overlay object but
makes no ioctl calls.

If the driver finds the frame, as a whole, to be not ok, the
validation fails and overlay/hwc return silently.

If a certain overlay object is mis-configured or pipes are
unavailable, the driver sets the number of objects it processed.
Overlay uses this to dump the incorrect config.

Change-Id: Ifb2b7fadc6bd6d9d94a35ba3908fbd832f41447f
hwc: Do not set a default DPI value

If the driver does not expose primary panel's physical
dimensions, do not assume a default DPI of 160. Instead,
set it to the default value specified in the build property.

Change-Id: If71e721f6a3fa5ece93c307f6e09b45d1ecafed4
h/q/d: Rename property to enable partial update

Rename property to enable partial update to keep within MAX
string length.

Change-Id: I16d09b49500f3cd996c66eb52aa80df3a5f62b27