[NFC][SampleFDO] Clean the unneeded field and the related loop (llvm#132376)

Clean the unneeded field 'TotalCollectedSamples' and the unnecessary
loop.
The field seems introduced in:https://reviews.llvm.org/D31952, and its
uses were removed in: https://reviews.llvm.org/D19287, but this field
and unnecessary calculation were not cleaned up.
This patch will remove these unneeded codes.

Author: Jinjie-Huang

llvm/lib/Transforms/IPO/SampleProfile.cpp

@@ -562,12 +562,6 @@ class SampleProfileLoader final : public SampleProfileLoaderBaseImpl<Function> {
   /// used to generate the current profile.
   std::shared_ptr<ProfileSymbolList> PSL;
 
-  /// Total number of samples collected in this profile.
-  ///
-  /// This is the sum of all the samples collected in all the functions executed
-  /// at runtime.
-  uint64_t TotalCollectedSamples = 0;
-
   // Information recorded when we declined to inline a call site
   // because we have determined it is too cold is accumulated for
   // each callee function. Initially this is just the entry count.
@@ -2183,10 +2177,6 @@ bool SampleProfileLoader::runOnModule(Module &M, ModuleAnalysisManager *AM,
       rejectHighStalenessProfile(M, PSI, Reader->getProfiles()))
     return false;
 
-  // Compute the total number of samples collected in this profile.
-  for (const auto &I : Reader->getProfiles())
-    TotalCollectedSamples += I.second.getTotalSamples();
-
   auto Remapper = Reader->getRemapper();
   // Populate the symbol map.
   for (const auto &N_F : M.getValueSymbolTable()) {