trusty: Increase limit on coverage counters

Keymaster has more than 4096 counters, so we need to allocate a larger
section for the libfuzzer extra counters. Increases the size of the
extra counters section to 16384.

Bug: 171750250
Test: atest libtrusty_coverage_test
Change-Id: Iaee2c74b6d0c7ae8a2e5a30525759f89f825a091