Update path to generic driver tests

After the recent Mbed OS folder restructuring, the CI for Mbed CLI fails
as the CI scripts contain hard-coded paths to locate the generic driver
tests. Update the CI scripts with the new path, so that CI has a chance
to pass with new versions of Mbed OS.

Author: Patater

.circleci/config.yml

@@ -72,7 +72,7 @@ commands:
                 command: |
                     echo $PATH
                     ls -l /opt/gcc-arm-none-eabi-5_3-2016q1/bin
-                    mbed compile --source=. --source=mbed-os/TESTS/mbed_drivers/generic_tests -j 0
+                    mbed compile --source=. --source=mbed-os/drivers/tests/TESTS/mbed_drivers/generic_tests -j 0
                     mbed test --compile -n mbed-os-tests-mbed_drivers-generic_tests -j 0
     run_old_support_tests:
         steps: