Create vsync_event sysfs entry, don't send 60hz uevent VEVENT= updates

Partially reverts
07e06c43d3cb67df84b37d58026a7ee3bc9e0019 msm_fb: fixes for SEMC panels and fb

Change-Id: I251ba2ab9dec3cbb74b506cf173d8759805d5a1c
Merge pull request #10 from mkj/cm-10.2

Avoid ueventd CPU spinning at 60hz for vsync