rocr: initialize 'data_rdy' & correct 'const' functions

'const' member functions have syntax errors and struct
'data_rdy' have uninitialized members

v1: correct misplaced 'const' for member functions
v2: add initialization for 'data_rdy' in constructor

Change-Id: I29bada475217c9df81f0d0400e7a3f44aa8afe0c
Signed-off-by: Apurv Mishra <apurv.mishra@amd.com>

runtime/hsa-runtime/pcs/pcs_runtime.cpp

@@ -131,6 +131,11 @@ PcsRuntime::PcSamplingSession::PcSamplingSession(
   csd.buffer_size = buffer_size;
   csd.data_ready_callback = data_ready_callback;
   csd.client_callback_data = client_callback_data;
+
+  data_rdy.buf1 = nullptr;
+  data_rdy.buf1_sz = 0;
+  data_rdy.buf2 = nullptr;
+  data_rdy.buf2_sz = 0;
 }
 
 void PcsRuntime::PcSamplingSession::GetHsaKmtSamplingInfo(HsaPcSamplingInfo* sampleInfo) {