Split Build: Enable IRQ Test suites

1. Add include directory within test Partitions directly to NS libraries
instead of linking the corresponding library as the library wouldn't be
available when building NS
2. Use TFM_PARTITION_xLIH_TEST in test Secure Partition building

Change-Id: Ia60aeef90e3e685893a0195a944e116b008fcc8f
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
7 files changed