tests: interrupt: Fix nested_irq test for Arm's GIC in Non-Secure state

Change SGI interrupt lines from 14-15 to 6-7 for nested interrupt
testing. SGI 8-15 are unaccessible from Non-Secure state (e.g., when
running with TF-A), causing test failures. SGI 0-2 are reserved for
Zephyr SMP IPIs, so use SGI 6-7 which work in both Secure and
Non-Secure configurations.

Fixes test failure: "isr0 did not execute" assertion at line 184.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
1 file changed