drm/amd/display: add missing void parameter to dc_create_transfer_func

Add a missing void parameter to function dc_create_transfer_func, fixes
sparse warning:

warning: non-ANSI function declaration of function 'dc_create_transfer_func'

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>