staging: vc04_services: Use __func__ macro

It's better to use the __func__ macro instead of open-code the function
name. This fixes the following checkpatch warning:

WARNING: Prefer using '"%s...", __func__' to using 'x',
this function's name, in a string

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>