ASoC: topology: Only use valid names of PCM for the kernel DAI & DAI link

User space may not always set a valid FE DAI driver's name, FE DAI link's
name, stream name or cpu DAI name. In such cases, there are all ZERO in
these name string buffers of a topology PCM object. This patch will only
duplicate valid name strings for kernel FE DAI driver and DAI link when
creating them from topology, and free the name strings when destroying
them.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>