selftests/efivarfs: add required kernel configs

BugLink: https://bugs.launchpad.net/bugs/1801900

[ Upstream commit 53cf59d6 ]

add config file
Signed-off-by: Lei Yang <Lei.Yang@windriver.com>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

tools/testing/selftests/efivarfs/config

+CONFIG_EFIVAR_FS=y