greybus: core: add device prefix to error messages

Use dev_err and dev_warn where appropriate and remove now unused pr_fmt
defines.

Testing Done:
Tested on DB3.5 with the generic bridge firmware on APB2.

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