media: siano: Drop unnecessary error check for debugfs_create_dir/file()

Both debugfs_create_dir() and debugfs_create_file() return ERR_PTR
and never return NULL.

As Hans suggested, this patch removes the error checking for both
debugfs_create_dir() and debugfs_create_file() in smsdvb_debugfs_create().
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.

And as Hans pointed out, it's much better to first allocate debug_data
before calling debugfs_create_dir, which need not to clean anything up in
that case.

Fixes: 503efe5c

 ("[media] siano: split debugfs code into a separate file")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>