Revert "fpc: keep fpc in system-background"

While Google found that fingerprint HAL is insensitive to
increased CPU throughput, we have not found that to be the
case and allowing more CPUs makes fingerprint unlock up to
2x faster in some tests.

This reverts commit d0fdb443.

Change-Id: I817f52e36530114cbd9185d88e44f38f379ff93b