wifi: mt76: Drop unnecessary error check for debugfs_create_dir()

debugfs_create_dir() returns ERR_PTR and never return NULL.

As Russell suggested, this patch removes the error checking for
debugfs_create_dir(). This is because the DebugFS kernel API is developed
in a way that the caller can safely ignore the errors that occur during
the creation of DebugFS nodes. The debugfs APIs have a IS_ERR() judge in
start_creating() which can handle it gracefully. So these checks are
unnecessary.

Fixes: 17f1de56 ("mt76: add common code shared between multiple chipsets")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Suggested-by: Russell King (Oracle) <linux@armlinux.org.uk>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/debugfs.c

@@ -109,8 +109,6 @@ mt76_register_debugfs_fops(struct mt76_phy *phy,
 	struct dentry *dir;
 
 	dir = debugfs_create_dir("mt76", phy->hw->wiphy->debugfsdir);
-	if (!dir)
-		return NULL;
 
 	debugfs_create_u8("led_pin", 0600, dir, &phy->leds.pin);
 	debugfs_create_u32("regidx", 0600, dir, &dev->debugfs_reg);