gpu.c: ppcg_transform_data: replace gpu_gen pointer by ppcg_kernel pointer
gpu.c: ppcg_transform_data: replace gpu_gen pointer by ppcg_kernel pointer

The only information we need from the gpu_gen structure is exactly
this ppcg_kernel pointer.

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

nicolasvasilache/ppcg,nicolasvasilache/ppcg,Meinersbur/ppcg,Meinersbur/ppcg