staging: gdm72xx: replace printk() and debug macros with dynamic debugging

Replace printk(KERN_DEBUG ...) with netdev_dbg and dev_dbg. Remove
debug macros which become unnecessary.

This removes the following types of checkpatch warnings from the driver:
drivers/staging/gdm72xx/gdm_sdio.c:461: WARNING: Prefer netdev_dbg(netdev, ... then dev_dbg(dev, ... then pr_debug(...  to printk(KERN_DEBUG ...

Signed-off-by: Kristina Martšenko <kristina.martsenko@gmail.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>