SystemUI: always use transparent notification shade

Devices with less than 512MB of memory have a solid
black notification shade. Remove the isHighEndGfx()
check to force a transparent notification shade on
all devices.

Change-Id: I9a68a2a8b0d36685f8899f3bbed43bb6bccb47b1

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java