usb: gadget: use %pm to print mac addresses

%pm already provides pretty print for mac addresses, let's
use that and drop homebrew mac address printing.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --cc drivers/usb/gadget/f_ecm.c
Simple merge

diff --cc drivers/usb/gadget/f_ncm.c
Simple merge

diff --cc drivers/usb/gadget/f_subset.c
Simple merge