greybus: svc: use a common prefix for debugfs functions

Use the common gb_svc functions also for the recently added svc
functions. Having a common prefix clearly signals where the code
resides, something which improves readability and helps during
debugging (e.g. stack traces).

Note that all functions in svc.c except for these three use the common
prefix with the exception of the pwr_debugfs callbacks (that still use
*a* common prefix) and the attribute accessors (than can not have a
common prefix due to some macro magic).

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>