Clarify unsigned int type in AIDL program id

Clarified that the value in ProgramIdentifier in AIDL broadcast radio
HAL should be unsigned 64-bit int, but is represented as signed int
since unsigned int types are not supported in AIDL.

Bug: 299489486
Test: m -j
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:40a58baa2cf0380dcab908a6f1e3cf8fd11d351c)
Merged-In: I2f35cefebdf1b5e39bf48cab896b077c4cb6c2e4
Change-Id: I2f35cefebdf1b5e39bf48cab896b077c4cb6c2e4
diff --git a/broadcastradio/aidl/android/hardware/broadcastradio/ProgramIdentifier.aidl b/broadcastradio/aidl/android/hardware/broadcastradio/ProgramIdentifier.aidl
index 2057d97..a2de5d6 100644
--- a/broadcastradio/aidl/android/hardware/broadcastradio/ProgramIdentifier.aidl
+++ b/broadcastradio/aidl/android/hardware/broadcastradio/ProgramIdentifier.aidl
@@ -30,8 +30,10 @@
     IdentifierType type = IdentifierType.INVALID;
 
     /**
-     * The uint64_t value field holds the value in format described in comments
-     * for IdentifierType enum.
+     * The value field holds the value in format described in comments for IdentifierType enum.
+     *
+     * The value should be 64-bit unsigned integer, but is represented as 64-bit signed integer
+     * in AIDL.
      */
     long value;
 }