Defer initialization for mEglConfigA8

This will only be used by some devices, when requested by SystemUI.
Defer initialization until its needed. This removes the unnecessary
ALOGE. If the device needs A8 and doesn't have it, it will still emit a
fatal log, which will enclude the EGL error.

Bug: 210501051
Test: make
Change-Id: I2c45d910a272e6bf434b8dae52da88fb927ac82a