Update vehicle hal usage comments

Fix typos and clarify a couple of sentences in the descriptive comments
associated with Vehicle HAL (especially with respect to AUDIO).

Test:  make -j40
Change-Id: If3bcb82a68d28c5560398174e5201227c15596d4
diff --git a/current.txt b/current.txt
index a5b5930..639b1a9 100644
--- a/current.txt
+++ b/current.txt
@@ -193,6 +193,7 @@
 760485232f6cce07f8bb05e3475509956996b702f77415ee5bff05e2ec5a5bcc android.hardware.dumpstate@1.0::IDumpstateDevice
 1fecfa1609ff9d27ebf761a84b4336efa9d5dac5b241f19a6663f70d8db2c4b1 android.hardware.radio@1.0::IRadioResponse
 28e929b453df3d9f5060af2764e6cdb123ddb893e3e86923c877f6ff7e5f02c9 android.hardware.wifi@1.0::types
+bfd81bcafa3c97519cd56ad29e9fa48e23d1d323b89dbcc85899282a8c628194 android.hardware.automotive.vehicle@2.0::types
 
 # HALs released in Android O MR1