Implement synchronous IN benchmarking

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Implement synchronous OUT benchmarking

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Allow specifying the transfer size

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Implement asynchronous IN/OUT benchmarking

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>