fstests: fix fstests_test_dev variable setting

commit 4947aef ("fstests: use selective yaml output on a
slew of different variables") removed FSTESTS_TEST_DEV variable setup
but the propagation for the variable to extra vars was still being
relied upon with:

FSTESTS_ARGS += fstests_test_dev='$(FSTESTS_TEST_DEV)'

Since FSTESTS_TEST_DEV is empty we were setting fstests_test_dev to
an empty string and the ansible task that ran gendisks.sh would fail.

Fix this by removing fstests_test_dev variable propagation using the
old scheme and just use selective yaml output with "output yaml" below
the symbol name on the respective Kconfig symbol declaration.

Reported-by: Carlos Maiolino <[email protected]>
Signed-off-by: Luis Chamberlain <[email protected]>

Author: mcgrof

workflows/fstests/Kconfig

@@ -601,6 +601,7 @@ endif # FSTESTS_TESTDEV_SPARSEFILE_GENERATION
 
 config FSTESTS_TEST_DEV
 	string "The device to use TEST_DEV on fstests"
+	output yaml
 	default "/dev/loop16" if FSTESTS_TESTDEV_SPARSEFILE_GENERATION
 	depends on FSTESTS_TESTDEV_SPARSEFILE_GENERATION
 	help

workflows/fstests/Makefile.sparsefiles

@@ -1,6 +1,5 @@
 FSTESTS_ARGS += fstests_testdev_sparsefile_generation='True'
 
-FSTESTS_ARGS += fstests_test_dev='$(FSTESTS_TEST_DEV)'
 FSTESTS_LOGWRITES_DEV:=$(subst ",,$(CONFIG_FSTESTS_LOGWRITES_DEV))
 FSTESTS_ARGS += fstests_logwrites_dev='$(FSTESTS_LOGWRITES_DEV)'