gpu.c: create_domain_leaf: handle domain leaves not inside any kernel
gpu.c: create_domain_leaf: handle domain leaves not inside any kernel

In the next commit, we will introduce the possibility of mapping
only part of the input scop to the device.  We therefore need to
adjust create_domain_leaf to take into account that some user
statements may be generated on the host, outside any kernel.

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

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