gallium/util: remove PIPE_THREAD_ROUTINE()

gallium/util: remove PIPE_THREAD_ROUTINE()

This was made unnecessary with fd33a6bcd7f12.

This was mostly done with:
find ./src -type f -exec sed -i -- \
's:PIPE_THREAD_ROUTINE(\([^,]*\), \([^)]*\)):int\n\1(void \*\2):g' {} \;

With some small manual tidy ups.

Reviewed-by: Plamena Manolova <plamena.manolova@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>