perf/x86/intel: Remove pointless tests

Both intel_commit_scheduling() and intel_get_excl_contraints() test
for cntr < 0.

The only way that can happen (aside from a bug) is through
validate_event(), however that is already captured by the
cpuc->is_fake test.

So remove these test and simplify the code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>