bna: Remove field bnad_dentry_files[] in struct bnad

bna: Remove field bnad_dentry_files[] in struct bnad

Function debugfs_remove() recursively removes a directory, include all
files created by debugfs_create_file(). Therefore, there is no need to
explicitly record each file with member ->bnad_dentry_files[] and
explicitly delete them at the end. Remove field bnad_dentry_files[] and
its related processing codes for simplification.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241028020943.507-3-thunder.leizhen@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>