arch: arm: aarch32: cortex_a_r: disable interrupts before context switching

Ultil now Cortex A/R aarch32 implementation for context
switching expects that interrupts was disabled. This is
true if a context switching happens at thread context.

But if a context switching happens at last action during
interrupt context, this assumption is not true because the
interrupts are still enabled (to allow nesting interrupts).

Disable interrupts at the last interrupt action to ensure
the interrupts are always disabled before context switching
is processed

Signed-off-by: Dat Nguyen Duy <dat.nguyenduy@nxp.com>