of: overlay: Fix kerneldoc warning in of_overlay_remove()

'*ovcs_id' causes a warning because '*' is treated as bold markup:

Documentation/devicetree/kernel-api:56: ../drivers/of/overlay.c:1184: WARNING: Inline emphasis start-string without end-string.

Fix this by using the normal '@' markup for function parameters. That
appears to be enough to keep the '*' from being interpretted as markup.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Frank Rowand <frowand.list@gmail.com>
Link: https://lore.kernel.org/r/20210421154548.1192903-1-robh@kernel.org/


Signed-off-by: Rob Herring <robh@kernel.org>