selftests: create test-specific kconfig fragments

Create the config file in each directory of testcase which need
more kernel configuration than the default defconfig. User could
use these configs with merge_config.sh script:

Enable config for specific testcase:
(export ARCH=xxx #for cross compiling)
./scripts/kconfig/merge_config.sh .config \
		tools/testing/selftests/xxx/config

Enable configs for all testcases:
(export ARCH=xxx #for cross compiling)
./scripts/kconfig/merge_config.sh .config \
		tools/testing/selftests/*/config
Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Reviewed-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/cpu-hotplug/config

+CONFIG_NOTIFIER_ERROR_INJECTION=y
+CONFIG_CPU_NOTIFIER_ERROR_INJECT=m

tools/testing/selftests/firmware/config

+CONFIG_TEST_FIRMWARE=y

tools/testing/selftests/ftrace/config

+CONFIG_FTRACE=y

tools/testing/selftests/ipc/config

+CONFIG_EXPERT=y
+CONFIG_CHECKPOINT_RESTORE=y

tools/testing/selftests/memory-hotplug/config

+CONFIG_MEMORY_HOTPLUG=y
+CONFIG_MEMORY_HOTPLUG_SPARSE=y
+CONFIG_NOTIFIER_ERROR_INJECTION=y
+CONFIG_MEMORY_NOTIFIER_ERROR_INJECT=m

tools/testing/selftests/mount/config

+CONFIG_USER_NS=y
+CONFIG_DEVPTS_MULTIPLE_INSTANCES=y

tools/testing/selftests/net/config

+CONFIG_USER_NS=y
+CONFIG_BPF_SYSCALL=y
+CONFIG_TEST_BPF=m

tools/testing/selftests/pstore/config

+CONFIG_MISC_FILESYSTEMS=y
+CONFIG_PSTORE=y
+CONFIG_PSTORE_PMSG=y
+CONFIG_PSTORE_CONSOLE=y

tools/testing/selftests/seccomp/config

+CONFIG_SECCOMP=y
+CONFIG_SECCOMP_FILTER=y

tools/testing/selftests/static_keys/config

+CONFIG_TEST_STATIC_KEYS=m

tools/testing/selftests/user/config

+CONFIG_TEST_USER_COPY=m

tools/testing/selftests/vm/config

+CONFIG_USERFAULTFD=y

tools/testing/selftests/zram/config

+CONFIG_ZSMALLOC=y
+CONFIG_ZRAM=m