* set gDeviceType in testharness.c, also moved gTestRounding to imageHelpers.cpp & .h and removed duplicate code from host_atomics.cpp
* Cleaned up some redundant code
* Reversed the change in testharness.c
Some of the setup functionality is already there in the test harness, so
use that and remove the duplicated code from within the suite.
Signed-off-by: Radek Szymanski <radek.szymanski@arm.com>