amd-xgbe: Avoid potential string truncation in name

Build with W=1 were warning about a potential string truncation:

drivers/net/ethernet/amd/xgbe/xgbe-drv.c: In function 'xgbe_alloc_channels':
drivers/net/ethernet/amd/xgbe/xgbe-drv.c:211:73: warning: '%u' directive output may be truncated writing between 1 and 10 bytes into a region of size 8 [-Wformat-truncation=]
  211 |                 snprintf(channel->name, sizeof(channel->name), "channel-%u", i);
      |                                                                         ^~
drivers/net/ethernet/amd/xgbe/xgbe-drv.c:211:64: note: directive argument in the range [0, 4294967294]
  211 |                 snprintf(channel->name, sizeof(channel->name), "channel-%u", i);
      |                                                                ^~~~~~~~~~~~
drivers/net/ethernet/amd/xgbe/xgbe-drv.c:211:17: note: 'snprintf' output between 10 and 19 bytes into a destination of size 16
  211 |                 snprintf(channel->name, sizeof(channel->name), "channel-%u", i);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Increase the size of the "name" buffer to handle the full format range.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312100937.ZPZCARhB-lkp@intel.com/
Cc: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231212221312.work.830-kees@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/amd/xgbe/xgbe.h

@@ -495,7 +495,7 @@ struct xgbe_ring {
  * a DMA channel.
  */
 struct xgbe_channel {
-	char name[16];
+	char name[20];
 
 	/* Address of private data area for device */
 	struct xgbe_prv_data *pdata;