Remove lock on MediaCrypto's decrypt call

The lock isn't necessary and prevents concurrent hwbinder
calls into the drm plugin which impacts performance.
Serialization of decrypt calls is done at a lower level.

bug: 157017229
test: Media GTS tests on coral
Change-Id: I38e3132f45c140cba9b2b8a72054fbff5eedb997
1 file changed