Remove redundant hotplug call

Initial hotplug state is reported back during callback registration, but during VTS tests we've noticed error that is caused by calling hotplug with same display twice.

HandleInitialHotplugState calls hotplug function for each connected display, so it covers HWC_DISPLAY_PRIMARY too, therefore first call should be removed, as it is redundant and causes minor error.

Smoke testing haven't found any new issues and running VtsHalGraphicsComposerV2_1Target shows that issue was fixed. VTS test results before proposed changes:

Module	Passed	Failed	Total Tests
arm64-v8a VtsHalGraphicsComposerV2_1Target	0	53	53
armeabi-v7a VtsHalGraphicsComposerV2_1Target	0	53	53

Vts test results after removing redundant hotplug call:

Module	Passed	Failed	Total Tests
arm64-v8a VtsHalGraphicsComposerV2_1Target	31	22	53
armeabi-v7a VtsHalGraphicsComposerV2_1Target	31	22	53