Staging: vt6655: Removal of Unused Function

This patch removes unused function 'RFbShutDown' from file rf.c

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>