gpu: host1x: Fix mask for syncpoint increment register

On Tegra186+, the syncpoint ID has 10 bits of space. To allow
using more than 256 syncpoints, fix the mask.

Fixes: 9abdd497

 ("gpu: host1x: Tegra234 device data and headers")
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>