ACPI / processor: Do not request ACPI cpufreq module directly

Function acpi_processor_load_module() used by the ACPI processor
driver can only really work if the acpi-cpufreq module is available
when acpi_processor_start() is executed which usually is not the case
for systems loading the processor driver module from an initramfs.

Moreover, that used to be a hackish workaround for module autoloading
issues, but udev loads acpi-cpufreq just fine nowadays, so that
function isn't really necessary any more.  For this reason, drop
acpi_processor_load_module() entirely.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>