staging:panel:panel.c Fix typo in staging:panel

The below patch fixes a typo I found while reading.

Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Cc: Willy Tarreau <willy@meta-x.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>