gpu: host1x: Fix _writel function declarations

Some of the _writel functions in dev.h had the r and v parameters
swapped. Fix this to avoid confusion.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240425050238.2943404-1-cyndis@kapsi.fi