ANDROID: recommended.cfg: Setup verity root A/B

While following A/B booting scheme, kernel needs to setup verity for
root(i.e. system) partition before mounting it. Enable the following
configs to do the same

CONFIG_DM_ANDROID_VERITY=y
CONFIG_ASYMMETRIC_KEY_TYPE=y
CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y
CONFIG_X509_CERTIFICATE_PARSER=y
CONFIG_PKCS7_MESSAGE_PARSER=y
CONFIG_PKCS7_TEST_KEY=y

Bug: 27175947

Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
Change-Id: Ic0625b721c9f3e47fad10c03a4841ca8a289ecbc