android: fiq_debugger: restrict access to critical commands.

Sysrq must be enabled via /proc/sys/kernel/sysrq as a security
measure to enable various critical fiq debugger commands that
either leak information or can be used as a system attack.

Default disabled, this will leave the reboot, reset, irqs, sleep,
nosleep, console and ps commands.  Reboot and reset commands
will be restricted from taking any parameters.  We will also
switch to showing the limited command set in this mode.

Bug: 32402555
Change-Id: I3f74b1ff5e4971d619bcb37a911fed68fbb538d5
Tracked-On: https://jira01.devtools.intel.com/browse/AW-4391


Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Reviewed-on: https://android.intel.com/569870


Reviewed-by: Louis, FabienX <fabienx.louis@intel.com>
Tested-by: Louis, FabienX <fabienx.louis@intel.com>
Reviewed-by: Dubray, SimonX <simonx.dubray@intel.com>
Reviewed-by: Akue, LoicX <loicx.akue@intel.com>
Reviewed-by: Tasayco Loarte, VictorX <victorx.tasayco.loarte@intel.com>