staging: vt6655: Rename function MACbSafeStop

Rename function MACbSafeStop to vt6655_mac_safe_stop to avoid CamelCase
which is not accepted by checkpatch.pl. Remove unnecessary declaration
of function and make function static.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/5c91b281dfab75e5ccf13413232ec993a8056af8.1662890990.git.philipp.g.hortmann@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>