Rename unused fields of RS base object handle in 64-bits

Fields other than the first one (p) in RS_BASE_OBJECT are set in some
part of existing RS runtime, but is not used at all. However, removing
them is not desirable as size of RS_BASE_OBJECT is really part of the
ABI and thus if we change it, we are creating a new ABI variant here,
which is not always desirable.

For example, consider a library that contains compiled scripts and
assuming we pass allocation handles between the library and other
user codes, changes to handle size only in user code would break the
compatibility on things like array of rs_allocations.

Thus, to keep ABI compatibility the unused fields r, v1, v2 are renamed.
Also they are now assigned zero consistently. These field however are
not copied consistently in the current runtime, and are not expected
so anyways.

Bug: 35043722
Test: mm, CTS and RSTest on Angler
Change-Id: I426fad8e07bf445b6d8625bd23c689acaee26322

driver/rsdBcc.cpp

diff --git a/driver/rsdBcc.cpp b/driver/rsdBcc.cpp
index d9aec53..0e07aaf 100644
--- a/driver/rsdBcc.cpp
+++ b/driver/rsdBcc.cpp
@@ -183,12 +183,8 @@
 {
     obj->p = script;
 #ifdef __LP64__
-    obj->r = nullptr;
-    if (script != nullptr) {
-        obj->v1 = script->mHal.drv;
-    } else {
-        obj->v1 = nullptr;
-    }
-    obj->v2 = nullptr;
+    obj->unused1 = nullptr;
+    obj->unused2 = nullptr;
+    obj->unused3 = nullptr;
 #endif
 }