hwmon: (pmbus/ucd9000) Drop unnecessary error check for debugfs_create_dir

hwmon: (pmbus/ucd9000) Drop unnecessary error check for debugfs_create_dir

This patch removes the error checking for debugfs_create_dir
in ucd9000.c. This is because the debugfs_create_dir() does not
return NULL but an ERR_PTR after an error.
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 Api handles
it gracefully. The check is unnecessary.

Link to the comment above debugfs_create_dir:
https://elixir.bootlin.com/linux/latest/source/fs/debugfs/inode.c#L565

Signed-off-by: Osama Muhammad <osmtendev@gmail.com>
Link: https://lore.kernel.org/r/20230526154906.6370-1-osmtendev@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>