Remove outdated doc on mbedtls_gcm_update()

Signed-off-by: Chien Wong <m@xv97.com>
diff --git a/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h b/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h
index e620be7..c27f2dc 100644
--- a/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h
+++ b/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h
@@ -264,22 +264,6 @@
  *                  decrypt. After the last part of the input, call
  *                  mbedtls_gcm_finish().
  *
- *                  This function may produce output in one of the following
- *                  ways:
- *                  - Immediate output: the output length is always equal
- *                    to the input length.
- *                  - Buffered output: the output consists of a whole number
- *                    of 16-byte blocks. If the total input length so far
- *                    (not including associated data) is 16 \* *B* + *A*
- *                    with *A* < 16 then the total output length is 16 \* *B*.
- *
- *                  In particular:
- *                  - It is always correct to call this function with
- *                    \p output_size >= \p input_length + 15.
- *                  - If \p input_length is a multiple of 16 for all the calls
- *                    to this function during an operation, then it is
- *                    correct to use \p output_size = \p input_length.
- *
  * \note            The output buffer \p output can be the same as the input
  *                  buffer \p input. If \p output is greater than \p input, they
  *                  cannot overlap.
@@ -293,7 +277,6 @@
  *                      is greater than zero, this must be a writable buffer of
  *                      of at least \p output_size bytes.
  * \param output_size   The size of the output buffer in bytes.
- *                      See the function description regarding the output size.
  * \param output_length On success, \p *output_length contains the actual
  *                      length of the output written in \p output.
  *                      On failure, the content of \p *output_length is