task-opie: provide defaults for screen resolution
task-opie: provide defaults for screen resolution

Some machine confg files (most notably qemuarm) do not provide
MACHINE_DISPLAY_WIDTH/HEIGHT_PIXELS values. Provide sane (QVGA) defaults
for those variables, as they are currently used only to select taskbar
images packet.

Signed-off-by: Dmitry Eremin-Solenikov <b6edad08270b2e4ffbcb0879e25a0e29a48c5275@gmail.com>
Signed-off-by: Paul Eggleton <737d4dae46a541673d7bf4e0d5b32714b16528d8@linux.intel.com>

bluelightning/meta-opie,bluelightning/meta-opie,bluelightning/meta-opie,bluelightning/meta-opie,bluelightning/meta-opie