libhwcomposer: screen refresh rate 60Hz

Change-Id: I10f7c08991661821a97c9f186ee01146388f670c
Signed-off-by: Tommy Alex <iptux7@gmail.com>
libhwcomposer: vsync only when screen is on

Change-Id: I78183a10a5c9db14d898dca4c8644524c345dcc8
Signed-off-by: Tommy Alex <iptux7@gmail.com>
libhwcomposer: suppress redundant vsync

vsync only when the framebuffer have been posted.
this will result in a dynamic vsync rate,
which will save some battery life

Change-Id: I9af94f96df67c2a9ba634f8af2cc3c32193bcd9f
Signed-off-by: Tommy Alex <iptux7@gmail.com>