nvic: Check for ARM and Thumb, instead of a test macro
nvic: Check for ARM and Thumb, instead of a test macro

In the definition of function for disabling/enabling interrupts,
check for the architecture compiled for and use "cpsie i", "cpsid i"
if it's ARM and Thumb. This is far from perfect, but I think this
check is better than the previous one.

google/cortex-demos,google/cortex-demos,google/cortex-demos,google/cortex-demos