selftests/efivarfs: add required kernel configs

[ Upstream commit 53cf59d6c0ad3edc4f4449098706a8f8986258b6 ]

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>