drm/rockchip: Fix a typo

Fix a typo in comments.

Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Kreimer <algonell@gmail.com>
Acked-by: Andy <Yan&lt;andyshrk@163.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240915123943.105118-1-algonell@gmail.com