[why]
add customizable log with a message input, which is for adding
test log in debugging as printf function in ETW.

[Usage]
EVENT_LOG_CUST_MSG1("TestLog","Hello World %d=0x%x", 123, pDC);
Signed-off-by: Chiawen Huang <chiawen.huang@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>