drivers: nfc: nfcsim: remove return value check of `dev_dir`

Smatch complains that:
nfcsim_debugfs_init_dev() warn: 'dev_dir' is an error pointer or valid

According to the documentation of the debugfs_create_dir() function,
there is no need to check the return value of this function.
Just delete the dead code.

Signed-off-by: Jianuo Kuang <[e-mail]>
Reviewed-by: Dongliang Mu <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/nfc/nfcsim.c

···
 	}
 
 	dev_dir = debugfs_create_dir(devname, nfcsim_debugfs_root);
-	if (!dev_dir) {
-		NFCSIM_ERR(dev, "Could not create debugfs entries for nfc%d\n",
-			   idx);
-		return;
-	}
 
 	debugfs_create_u8("dropframe", 0664, dev_dir, &dev->dropframe);
 }