Revert "debugfs: more tightly restrict default mount mode"

This reverts commit 82aceae4.

The wlan module makes some debugfs directories when it is loaded.
Android userspace loads the wlan module as the system user and
the system user doesn't have write access to the debugfs
filesystem because the default permissions for debugfs are 0700
now. Revert this patch to allow the wlan module to create
directories in debugfs and successfully probe.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>