For me, this works:
cell = torch.nn.GRUCell(5,5).cuda()
h = torch.autograd.Variable(torch.rand(1,5)).cuda()
x = torch.autograd.Variable(torch.rand(1,5)).cuda()
cell(x,h)

`Variable containing:
0.3778 -0.1668  0.7313  0.4934  0.0283
[torch.cuda.FloatTensor of size 1x5 (GPU 0)]