Reduce multiple oem_ibm entry points in pldmd

Abstract the custom method of `OEM-IBM` into the oem-ibm.hpp file
to prevent the continuous increase of custom code and reduce multiple
`OEM-IBM` entry points in pldmd.

Tested: enabled oem-ibm and built pldm successfully.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Ieddb8d12281553e70bdb1c333bd29425c9d14fb0
diff --git a/libpldmresponder/test/libpldmresponder_pdr_sensor_test.cpp b/libpldmresponder/test/libpldmresponder_pdr_sensor_test.cpp
index 92da066..ae1ed3a 100644
--- a/libpldmresponder/test/libpldmresponder_pdr_sensor_test.cpp
+++ b/libpldmresponder/test/libpldmresponder_pdr_sensor_test.cpp
@@ -36,7 +36,7 @@
     auto event = sdeventplus::Event::get_default();
     Handler handler(&mockedUtils, 0, nullptr, "./pdr_jsons/state_sensor/good",
                     inPDRRepo, nullptr, nullptr, nullptr, nullptr, nullptr,
-                    nullptr, event);
+                    event);
     handler.getPDR(req, requestPayloadLength);
     Repo inRepo(inPDRRepo);
     getRepoByType(inRepo, outRepo, PLDM_STATE_SENSOR_PDR);
@@ -88,7 +88,7 @@
     auto event = sdeventplus::Event::get_default();
     Handler handler(&mockedUtils, 0, nullptr, "./pdr_jsons/state_sensor/good",
                     inPDRRepo, nullptr, nullptr, nullptr, nullptr, nullptr,
-                    nullptr, event);
+                    event);
     handler.getPDR(req, requestPayloadLength);
     Repo inRepo(inPDRRepo);
     getRepoByType(inRepo, outRepo, PLDM_STATE_SENSOR_PDR);