Remove DispSync default value/docs

Moves DispSync phase offset default values and documentation to
frameworks/native/services/surfaceflinger/Android.mk.

Bug: 30801895
Change-Id: I44a4355b2d112561b94ccfc6e9c3365885c205ad

target/board/generic/BoardConfig.mk

@@ -45,28 +45,6 @@ BUILD_EMULATOR_OPENGL := true
 # the GLES renderer disables itself if host GL acceleration isn't available.
 USE_OPENGL_RENDERER := true
 
-# Set the phase offset of the system's vsync event relative to the hardware
-# vsync. The system's vsync event drives Choreographer and SurfaceFlinger's
-# rendering. This value is the number of nanoseconds after the hardware vsync
-# that the system vsync event will occur.
-#
-# This phase offset allows adjustment of the minimum latency from application
-# wake-up (by Choregographer) time to the time at which the resulting window
-# image is displayed.  This value may be either positive (after the HW vsync)
-# or negative (before the HW vsync).  Setting it to 0 will result in a
-# minimum latency of two vsync periods because the app and SurfaceFlinger
-# will run just after the HW vsync.  Setting it to a positive number will
-# result in the minimum latency being:
-#
-#     (2 * VSYNC_PERIOD - (vsyncPhaseOffsetNs % VSYNC_PERIOD))
-#
-# Note that reducing this latency makes it more likely for the applications
-# to not have their window content image ready in time.  When this happens
-# the latency will end up being an additional vsync period, and animations
-# will hiccup.  Therefore, this latency should be tuned somewhat
-# conservatively (or at least with awareness of the trade-off being made).
-VSYNC_EVENT_PHASE_OFFSET_NS := 0
-
 TARGET_USERIMAGES_USE_EXT4 := true
 BOARD_SYSTEMIMAGE_PARTITION_SIZE := 1879048192  # 1.75 GB
 BOARD_USERDATAIMAGE_PARTITION_SIZE := 576716800