drm/tegra: hub: Increase buffer size to ensure all possible values can be stored

When converting from int to string, we must allow for up to 10-chars (2147483647).

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/tegra/hub.c: In function ‘tegra_display_hub_probe’:
 drivers/gpu/drm/tegra/hub.c:1106:47: warning: ‘%u’ directive output may be truncated writing between 1 and 10 bytes into a region of size 4 [-Wformat-truncation=]
 drivers/gpu/drm/tegra/hub.c:1106:42: note: directive argument in the range [0, 4294967294]
 drivers/gpu/drm/tegra/hub.c:1106:17: note: ‘snprintf’ output between 6 and 15 bytes into a destination of size 8

Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230824073710.2677348-16-lee@kernel.org