docs: power: Fix footnote reference for Toshiba Satellite P10-554

Sphinx reports unreferenced footnote warning on "Video issues with S3
resume" doc:

Documentation/power/video.rst:213: WARNING: Footnote [#] is not referenced. [ref.footnote]

Fix the warning by separating footnote reference for Toshiba Satellite
P10-554 by a space.

Fixes: 151f4e2b ("docs: power: convert docs to ReST and rename to *.rst")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/linux-next/20250122170335.148a23b0@canb.auug.org.au/


Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250122143456.68867-4-bagasdotme@gmail.com