firmware: fix typo on pr_info_once() when ignore_sysfs_fallback is used

When the sysctl knob is used ignore the fallback mechanism we pr_info_once()
to ensure its noted the knob was used. The print incorrectly states its a
debugfs knob, its a sysctl knob, so correct this typo.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>