Apply constexpr on global constant varaibles

When HIP_ENABLE_DEFERRED_LOADING=0, many global variables will be
referenced but they are not initialized in that early time. The patch
will use constexpr to initialze global constant varables in compile
time.

Change-Id: I9d538b7abc6a0ce700ec3332b97fc144db5fc1ef

rocclr/device/rocm/rocvirtual.cpp

@@ -65,28 +65,28 @@ namespace roc {
 // (HSA_FENCE_SCOPE_SYSTEM << HSA_PACKET_HEADER_RELEASE_FENCE_SCOPE) invalidates L1, L2 and flushes
 // L2
 
-static const uint16_t kInvalidAql =
+static constexpr uint16_t kInvalidAql =
     (HSA_PACKET_TYPE_INVALID << HSA_PACKET_HEADER_TYPE);
 
-static const uint16_t kBarrierPacketHeader =
+static constexpr uint16_t kBarrierPacketHeader =
     (HSA_PACKET_TYPE_BARRIER_AND << HSA_PACKET_HEADER_TYPE) | (1 << HSA_PACKET_HEADER_BARRIER) |
     (HSA_FENCE_SCOPE_SYSTEM << HSA_PACKET_HEADER_ACQUIRE_FENCE_SCOPE) |
     (HSA_FENCE_SCOPE_SYSTEM << HSA_PACKET_HEADER_RELEASE_FENCE_SCOPE);
 
-static const uint16_t kBarrierPacketAcquireHeader =
+static constexpr uint16_t kBarrierPacketAcquireHeader =
     (HSA_PACKET_TYPE_BARRIER_AND << HSA_PACKET_HEADER_TYPE) | (1 << HSA_PACKET_HEADER_BARRIER) |
     (HSA_FENCE_SCOPE_SYSTEM << HSA_PACKET_HEADER_ACQUIRE_FENCE_SCOPE) |
     (HSA_FENCE_SCOPE_NONE << HSA_PACKET_HEADER_RELEASE_FENCE_SCOPE);
 
-static const uint16_t kBarrierPacketReleaseHeader =
+static constexpr uint16_t kBarrierPacketReleaseHeader =
     (HSA_PACKET_TYPE_BARRIER_AND << HSA_PACKET_HEADER_TYPE) | (1 << HSA_PACKET_HEADER_BARRIER) |
     (HSA_FENCE_SCOPE_NONE << HSA_PACKET_HEADER_ACQUIRE_FENCE_SCOPE) |
     (HSA_FENCE_SCOPE_SYSTEM << HSA_PACKET_HEADER_RELEASE_FENCE_SCOPE);
 
-static const hsa_barrier_and_packet_t kBarrierAcquirePacket = {
+static constexpr hsa_barrier_and_packet_t kBarrierAcquirePacket = {
     kBarrierPacketAcquireHeader, 0, 0, {{0}}, 0, {0}};
 
-static const hsa_barrier_and_packet_t kBarrierReleasePacket = {
+static constexpr hsa_barrier_and_packet_t kBarrierReleasePacket = {
     kBarrierPacketReleaseHeader, 0, 0, {{0}}, 0, {0}};
 
 double Timestamp::ticksToTime_ = 0;