Change initialize libdrm device and file descriptor initialization
to use new APIs from Thunk. Libdrm recommends that we re-use the same
file descriptor thoughout the life of a process instead of re-creating
new one each time.
This is part of patch series for Virtual Memory API.
Change-Id: I1c0b8d1bd660cd25478b5f94c84071b90d93fc6c
David Yat Sin
a55f11025b