EGL: Do not look up default namespace when sphal is defined

If sphal name space exists, try to load drivers from sphal.
This patch stops loading the driver if it fails to find the driver
from sphal, instead of falling back to the default namespace.

Bug: 38435840
Test: sailfish builds and boots
Change-Id: Ib8ba73f57aa25431c4a2efe7c61a3699237cc3d2
Merged-In: Ib8ba73f57aa25431c4a2efe7c61a3699237cc3d2
(cherry picked from commit b732030e)