drm: writeback: Fix kernel doc name

drm: writeback: Fix kernel doc name

During the creation of drmm_ variants for writeback connector, one
function was renamed, but not the kernel doc.

To remove the warning, use the proper name in kernel doc.

Fixes: 135d8fc7af44 ("drm: writeback: Create an helper for drm_writeback_connector initialization")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/all/20250207142201.550ce870@canb.auug.org.au/
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250207-b4-fix-warning-v1-1-b4964beb60a3@bootlin.com
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>