Add Audio HAL V6 hashes to current.txt

Done using the following command:

hidl-gen -L hash -r android.hardware:hardware/interfaces \
   -r android.hidl:system/libhidl/transport \
   android.hardware.audio@6.0 \
   android.hardware.audio.common@6.0 \
   android.hardware.audio.effect@6.0

Bug: 138747770
Test: N/A
Change-Id: I9cbd5c2358a663ec346d8624d0e6a12c643147e3