At zcull bind we disable whole GR engine. This is unnecessary, so
instead disable only the channel and make sure it's unloaded.
Introduces also an API in fifo_gk20a.c to do the channel disable.
gr_gk20a_ctx_zcull_setup() was always passed true as last parameter,
so remove parameter.
Change-Id: I7ae6e101ec7d1ab3f6ee4e9bcc442d23dbd21247
Signed-off-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-on: http://git-master/r/787570