We dont need to set the functions to NULL which arent
needed as global structure members are by default
set to zero or NULL for pointers.

Cc: Leo Liu <leo.liu@amd.com>
Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>