add capsule describe
add capsule describe

Change-Id: I9ac587fd04f5d52bafb37f67c62454e627a5a31a
Signed-off-by: Kevin Zhao <9fc648be98fc18cb4028b7c8c8516da572477616@arm.com>

kevin-zhaoshuai/zun,kevin-zhaoshuai/zun,kevin-zhaoshuai/zun