ACPI: CPPC: Check cpc_read() return values consistently

ACPI: CPPC: Check cpc_read() return values consistently

Callers of cpc_read() ignore its return value, which can lead
to using uninitialized or stale values when the read fails.

Fix this by consistently checking cpc_read() return values in
cppc_get_perf_caps(), cppc_get_perf_ctrs(), and cppc_get_perf().

Link: https://lore.kernel.org/lkml/48bdf87e-39f1-402f-a7dc-1a0e1e7a819d@nvidia.com/
Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Link: https://patch.msgid.link/20260318095005.2437960-1-sumitg@nvidia.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>