Remove unnecessary property query.

With adding HAL interface to replace aaudio system property, the
functions of querying system property is useless. The removed functions
include:
  - AAudioProperty_getMMapPolicy
  - AAudioProperty_getMMapExclusivePolicy
  - AAudioProperty_getMixerBursts
  - AAudioProperty_getHardwareBurstMinMicros

Test: atest AAudioTests
Bug: 193275465
Change-Id: Ia7b6c8bc00498c87d68307657761753e0c383b57