[Coverity] Potential return value integer overflow in XPTI

[AlexeySachkov]

See Coverity issues at https://scan.coverity.com/projects/intel-llvm?tab=overview

CID 525275:

llvm/xptifw/src/xpti_trace_framework.cpp

Lines 2096 to 2098 in 8ea381f

	uint8_t registerStream(const char *StreamName) {
	return (uint8_t)MStreamStringTable.add(StreamName);
	}

CID 525261:

llvm/xptifw/src/xpti_trace_framework.cpp

Lines 2112 to 2114 in 8ea381f

	uint8_t registerVendor(const char *StreamName) {
	return (uint8_t)MVendorStringTable.add(StreamName);
	}

The table we are inserting into is xpti::StringTable in both cases and its add method returns xpti::string_id_t which is defined as int32_t.

Therefore, there could be an overflow resulting in an invalid ID received by callers of those register functions.