staging: vt6655: kernel style cleanup of mac.c

This patch removes from mac.c the file name and an ftrace-like pr_debug
per checkpatch's two warnings.

Signed-off-by: Lucas Henneman <lucas.henneman@linaro.org>
Link: https://lore.kernel.org/r/20210723144340.15787-13-lucas.henneman@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>