Crypto: Change to stateless service

Crypto service does not require a client to call to psa_connect()
or psa_close(). Instead the service can use a stateless mechanism.
Related documents are also updated.

Note: Framework version of Crypto partition has been updated to 1.1,
but not all features of FF-M 1.1 are implemented now.

Change-Id: Iad628667e4b63e809c933fb263734403c6274bf9
Signed-off-by: Summer Qin <summer.qin@arm.com>