libdrm: annotate public functions

This was done with:
nm --dynamic --defined-only build/libdrm.so | \
	grep " T " | \
	grep -v _fini | grep -v _init | \
	cut -d' ' -f3 > /tmp/a.txt

while read sym; do
	read f func line _ <<<$(cscope -d -L -1 $sym)
	if [ ! -z "$f" ]; then
		sed -i "${line}s/^/drm_public /" $f
	fi
done < /tmp/a.txt

Then the alignment of function arguments were manually fixed all over.
The idea here will be to switch the default visibility to hidden so we
don't export symbols we shouldn't.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>