mips: txx9: remove left-over for removed TXX9_ACLC configs

mips: txx9: remove left-over for removed TXX9_ACLC configs

The patch series "Remove support for TX49xx" (see Link) was only partially
applied: The ASoC driver was removed with commit a8644292ea46 ("ASoC:
txx9: Remove driver"), which was patch 10/10 from that series. The mips
architecture code to be removed with patch 1/10 from that series was not
applied.

This partial patch series application leaves the build config setup and
code in the mips architecture in a slightly unclean, intermediate state.
The configs HAS_TXX9_ACLC and SND_SOC_TXX9ACLC were removed, but are still
referenced in the txx9-architecture Kconfig and generic setup.

The script ./scripts/checkkconfigsymbols.py warns about this:

  HAS_TXX9_ACLC
  Referencing files: arch/mips/txx9/Kconfig

  SND_SOC_TXX9ACLC
  Referencing files: arch/mips/txx9/generic/setup.c

Clean up the code for those removed references.

Link: https://lore.kernel.org/all/20210105140305.141401-1-tsbogend@alpha.franken.de/
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>