1. Added negative test for hipDeviceGetAttribute
2. Fixed hipDeviceGetAttribute if int ptr input is null
Change-Id: I0e31f50fa407701fddf96e4eb64a87a371ff5d95
1. Added fallback for nullptr to hipGetDeviceProperties and hipGetDeviceCount
2. Added negative tests for hipGetDeviceProperties and hipGetDeviceCount
Change-Id: Iac93fd53d7d4794fb10546ddadf6ca802b047c87