dmadev: add telemetry

dmadev: add telemetry

Telemetry commands are now registered through the dmadev library
for the gathering of DSA stats. The corresponding callback
functions for listing dmadevs and providing info and stats for a
specific dmadev are implemented in the dmadev library.

An example usage can be seen below:

Connecting to /var/run/dpdk/rte/dpdk_telemetry.v2
{"version": "DPDK 22.03.0-rc2", "pid": 2956551, "max_output_len": 16384}
Connected to application: "dpdk-dma"
--> /
{"/": ["/", "/dmadev/info", "/dmadev/list", "/dmadev/stats", ...]}
--> /dmadev/list
{"/dmadev/list": [0, 1]}
--> /dmadev/info,0
{"/dmadev/info": {"name": "0000:00:01.0", "nb_vchans": 1, "numa_node": 0,
"max_vchans": 1, "max_desc": 4096, "min_desc": 32, "max_sges": 0,
"capabilities": {"mem2mem": 1, "mem2dev": 0, "dev2mem": 0, ...}}}
--> /dmadev/stats,0,0
{"/dmadev/stats": {"submitted": 0, "completed": 0, "errors": 0}}

Signed-off-by: Sean Morrissey <sean.morrissey@intel.com>
Reviewed-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: Conor Walsh <conor.walsh@intel.com>
Tested-by: Sunil Pai G <sunil.pai.g@intel.com>
Tested-by: Kevin Laatz <kevin.laatz@intel.com>
Acked-by: Chengwen Feng <fengchengwen@huawei.com>