drm/amdkfd: Define config HSA_AMD_P2P to support peer-to-peer

Extend current kernel config requirements of amdgpu by adding config
HSA_AMD_P2P. Enabling HSA_AMD_P2P is REQUIRED to support peer-to-peer
communication between AMD GPU devices over PCIe bus

Signed-off-by: Ramesh Errabolu <Ramesh.Errabolu@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>