NHLT fetch based on _DSM prevents ACPI table override mechanism from
being utilized. Make use of acpi_get_table to enable it and get rid of
redundant code. In consequence, NHLT can be overridden just like any
other ACPI table, e.g.: DSDT or SSDT.

Change has been verified on all Intel AVS architecture platforms, RVP
and production laptops both.

Change possible due to addition of NHLT signature to the list of
standard ACPI tables:
https://patchwork.kernel.org/patch/11463235/

Override helps not only with debug purposes but also allows user for
table adjustment when one found on their production hardware is invalid.
Shared official NHLT spec is now available to community at:
https://01.org/blogs/intel-smart-sound-technology-audio-dsp

NHLT support for iASL is still ongoing subject but should be available
in nearest future.
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lore.kernel.org/r/20200423160310.28019-1-cezary.rojewski@intel.comSigned-off-by: Takashi Iwai <tiwai@suse.de>