perf/x86: Remove stale fixed counter helper and fix hybrid PMU access

On hybrid systems, init_hw_perf_events() can call check_hw_exists() with
the global PMU pointer after perf_is_hybrid is set. In that case,
fixed_counter_disabled() uses hybrid() on a non-hybrid PMU object, so the
intel_ctrl access is taken from the wrong layout and can read out of
bounds.

fixed_counter_disabled() was added in commit 32451614da2a
("perf/x86/intel: Support CPUID 10.ECX to disable fixed counters"), when
fixed counters were tracked via num_fixed_counters. Today fixed counters
are represented by fixed_cntr_mask, so this helper is obsolete.

Remove fixed_counter_disabled() and its callers, and rely directly on the
fixed-counter bitmask. With the helper gone, check_hw_exists() no longer
needs a PMU argument, so drop that parameter as well. This removes the
invalid hybrid access and closes the out-of-bounds read risk.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Falcon <thomas.falcon@intel.com>
Reviewed-by: Zide Chen <zide.chen@intel.com>
Link: https://patch.msgid.link/20260717080342.1879573-6-dapeng1.mi@linux.intel.com

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