drm/tegra: Mark nvdec_writel() as inline

Without CONFIG_IOMMU_API, the nvdec_writel() function is unused, causing
a warning:

drivers/gpu/drm/tegra/nvdec.c:48:13: error: 'nvdec_writel' defined but not used [-Werror=unused-function]
   48 | static void nvdec_writel(struct nvdec *nvdec, u32 value, unsigned int offset)
      |             ^~~~~~~~~~~~

As this is a trivial wrapper around an inline function, mark it as
inline itself, which avoids the warning as well.

Fixes: e76599df354d ("drm/tegra: Add NVDEC driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/nvdec.c

@@ -45,7 +45,8 @@ static inline struct nvdec *to_nvdec(struct tegra_drm_client *client)
 	return container_of(client, struct nvdec, client);
 }
 
-static void nvdec_writel(struct nvdec *nvdec, u32 value, unsigned int offset)
+static inline void nvdec_writel(struct nvdec *nvdec, u32 value,
+				unsigned int offset)
 {
 	writel(value, nvdec->regs + offset);
 }