rocr: Fix inefficient copy operations

Refactor variable assignments to use std::move() where appropriate.
Updat function headers to accept parameters by const& where appropriate.

Signed-off-by: Alysa Liu <Alysa.Liu@amd.com>


[ROCm/ROCR-Runtime commit: f6c8cbd293]

projects/rocr-runtime/runtime/hsa-runtime/core/driver/kfd/amd_kfd_driver.cpp

@@ -83,7 +83,7 @@ __forceinline uint64_t drm_perm(hsa_access_permission_t perm) {
 
 } // namespace
 
-KfdDriver::KfdDriver(std::string& devnode_name)
+KfdDriver::KfdDriver(std::string devnode_name)
     : core::Driver(core::DriverType::KFD, std::move(devnode_name)) {}
 
 hsa_status_t KfdDriver::Init() {
@@ -128,8 +128,7 @@ hsa_status_t KfdDriver::ShutDown() {
 }
 
 hsa_status_t KfdDriver::DiscoverDriver(std::unique_ptr<core::Driver>& driver) {
-  std::string devnode("/dev/kfd");
-  auto tmp_driver = std::unique_ptr<core::Driver>(new KfdDriver(devnode));
+  auto tmp_driver = std::unique_ptr<core::Driver>(new KfdDriver("/dev/kfd"));
 
   if (tmp_driver->Open() == HSA_STATUS_SUCCESS) {
     driver = std::move(tmp_driver);

projects/rocr-runtime/runtime/hsa-runtime/core/inc/amd_kfd_driver.h

@@ -69,7 +69,7 @@ namespace AMD {
 /// and more.
 class KfdDriver final : public core::Driver {
 public:
-  KfdDriver(std::string& devnode_name);
+  KfdDriver(std::string devnode_name);
 
   /// @brief Determine of the KFD is present on the system and attemp to open it if found.
   ///