debugfs: Remove redundant access mode checks

debugfs: Remove redundant access mode checks

debugfs_get_tree() can only be called if debugfs itself calls
simple_pin_fs() or register_filesystem(), and those call paths also
check the access mode.

debugfs_start_creating() checks the access mode so the checks in the
debugfs_create_* functions are unnecessary.

An upcoming change will affect debugfs_allow, so doing this cleanup
first will make that change simpler.

Signed-off-by: Aaron Thompson <dev@aaront.org>
Link: https://patch.msgid.link/20251120102222.18371-2-dev@null.aaront.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>