lavu/opencl: apply misc cosmetics fixes

Split long lines, reindent code, add missing spaces between operators,
remove possibly confusing comment from av_opencl_buffer_read_image()
doxy, and use designated initializers for openclutils_class.
lavu/opencl: use consistent inclusion header guard name
ffplay: use seek per time for ogg by default

Fixes Ticket2383

Reviewed-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>