drm/gma500: Fix spelling mistake "patter" -> "pattern"

There is a spelling mistake in a DRM_DEBUG_KMS message. Fix it.

Reviewed-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240314163511.2372458-1-colin.i.king@gmail.com