The interrupt controller shutdown path does not need to save the mask of
enabled interrupts because the next state the system is going to be in is
akin to a cold boot, or a kexec'd kernel. Saving the mask only makes sense
if the software state needs to preserve the hardware state across a system
suspend/resume cycle.

As an optimization, and given that there are systems with dozens of such
interrupt controller, save a "slow" memory mapped I/O read in the shutdown
path where no saving/restoring is required.
Reported-by: Tim Ross <tim.ross@broadcom.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240424175732.1526531-1-florian.fainelli@broadcom.com