media: aspeed: Drop unnecessary error check for debugfs_create_file()

debugfs_create_file() return ERR_PTR and never return NULL.

When calling debugfs functions, there is no need to ever check the
return value. The function can work or not, but the code logic should
never do something different based on this.

Fixes: 52fed10a ("media: aspeed: add debugfs")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>