keymaster: spec does not require that update produce output

Remove out of spec enforcement on the amount of data returned
by update, as this is not specified in the HAL.

Bug: 109771020
Test: yes it is
Merged-In: Ic41afbd01d51faf48d3c0fe090409ebcd257cc1e
Change-Id: Ic41afbd01d51faf48d3c0fe090409ebcd257cc1e
(cherry picked from commit 7b75f015)