profiler: Reenable built-in profiler

profiler: Reenable built-in profiler

2ed1ebcf6 "timer: replace time() with QEMU_CLOCK_HOST" broke compile
when configured with --enable-profiler. Turned out the profiler has been
broken for a while.

This does s/qemu_time/tcg_time/ as the profiler only works in a TCG mode.
This also fixes the compile error.

This changes profile_getclock() to return nanoseconds rather than
CPU ticks as the "profile" HMP command prints seconds and there is no
platform-independent way to get ticks-per-second rate.
Since TCG is quite slow and get_clock() returns nanoseconds (fine
enough), this should not affect precision much.

This removes unused qemu_time_start and tlb_flush_time.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-Id: <1426478258-29961-1-git-send-email-aik@ozlabs.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>