SF: Reduce resync samples without present

Reduces the number of resync samples that DispSync will attempt to
collect without an intervening present from 12 to 4. The former value
was causing excessive power draw for some vendors' implementations, and
reducing it doesn't seem to harm anything.

Bug: 20724456
Change-Id: Ifd6e0490be67756ed001d509a38e8a36953b4618