Correct and clarify the documentation of GCM whole-message functions
Correct and clarify the documentation of GCM whole-message functions

Clarify the roles of the buffer parameter and their sizes.

Remove a statement about input size restrictions that only applies to
mbedtls_gcm_update, not to the whole-message functions.

Document the possible error codes.

Warn that mbedtls_gcm_crypt_and_tag in decrypt mode does not
authenticate the data and recommend using mbedtls_gcm_auth_decrypt
instead.

Mbed-TLS/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls