[hsa-runtime] Add support to hsa-runtime to find symbols from ".dynsym" section.

Earlier, hsa-runtime was unable to find symbols from a stripped ELF-image becasue
no support to find symbols from ".dynsym" section.

Looking for symbols in .dynsym is enabled by LOADER_USE_DYNSYM=1
environment variable

Change-Id: I4f0e8dd0eb053a6066d4d49b670c52e51149531a

runtime/hsa-runtime/libamdhsacode/amd_hsa_code.cpp

@@ -1765,8 +1765,8 @@ namespace code {
           hsatext = sec;
         }
       }
-      for (size_t i = 0; i < img->symtab()->symbolCount(); ++i) {
-        amd::elf::Symbol* elfsym = img->symtab()->symbol(i);
+      for (size_t i = 0; i < img->getSymbolTable()->symbolCount(); ++i) {
+        amd::elf::Symbol* elfsym = img->getSymbolTable()->symbol(i);
         Symbol* sym = 0;
         switch (elfsym->type()) {
         case STT_AMDGPU_HSA_KERNEL: {