Revert "[lldb] Allow fetching of RA register when above fault handler (llvm#98566)"

This reverts commit fd42417.

This patch has two problems.  First, it is unnecessary, Pavel landed
a fix a week or so before mine which solves this problem in
bbd54e0 .  Second, the fix is
incorrect; for a function above a trap handler, where all registers
are available, this patch would have lldb fetch the return address
register from frame 0.  This might be 10 frames up in the stack;
the frame 0 return address register is incorrect.  The change would
have been correct a short bit later than this, but Pavel's fix is
executed earlier in the function and none of this is needed.

(cherry picked from commit d29a50f)

Author: jasonmolenda

lldb/source/Target/RegisterContextUnwind.cpp

@@ -1402,7 +1402,7 @@ RegisterContextUnwind::SavedLocationForRegister(
       // it's still live in the actual register. Handle this specially.
 
       if (!have_unwindplan_regloc && return_address_reg.IsValid() &&
-          BehavesLikeZerothFrame()) {
+          IsFrameZero()) {
         if (return_address_reg.GetAsKind(eRegisterKindLLDB) !=
             LLDB_INVALID_REGNUM) {
           lldb_private::UnwindLLDB::ConcreteRegisterLocation new_regloc;