ASoC: mediatek: mt8192: Fix build failure

A build of arm64 allmodconfig with next-20201105 fails with the error:
ERROR: modpost: "mt8192_afe_gpio_request" undefined!
ERROR: modpost: "mt8192_afe_gpio_init" undefined!

Export the symbols so that mt8192-mt6359-rt1015-rt5682.ko finds it.

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lore.kernel.org/r/20201105124747.18383-1-sudipm.mukherjee@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>