Platform: Nordic: Fix IRQ test config

It might be a mistake brought by
I6ec4eb80363cdb6c62b7e1c8391a8c9265f6e477.

Change-Id: I5d5bdfddc251da5a369e407c754da22e9f532cf5
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
diff --git a/platform/ext/target/nordic_nrf/common/core/config.cmake b/platform/ext/target/nordic_nrf/common/core/config.cmake
index 8d0591b..689497e 100644
--- a/platform/ext/target/nordic_nrf/common/core/config.cmake
+++ b/platform/ext/target/nordic_nrf/common/core/config.cmake
@@ -8,8 +8,8 @@
 #
 #-------------------------------------------------------------------------------
 
-set(PLATFORM_SLIH_IRQ_TEST_SUPPORT)
-set(PLATFORM_FLIH_IRQ_TEST_SUPPORT)
+set(PLATFORM_SLIH_IRQ_TEST_SUPPORT    ON)
+set(PLATFORM_FLIH_IRQ_TEST_SUPPORT    ON)
 
 set(HAL_NORDIC_PATH "DOWNLOAD" CACHE PATH "Path to the Nordic HAL (or DOWNLOAD to fetch automatically)")
 set(HAL_NORDIC_VERSION "nrfx-3.0.0" CACHE STRING "Version of the Nordic HAL to download")