cpufreq: intel_pstate: Relocate platform preference check

Move the invocation of intel_pstate_platform_pwr_mgmt_exists() before
checking whether or not HWP is enabled because it does not depend on
any code running before it except for the vendor check and if CPU
performance scaling is going to be carried out by the platform, all of
the code that runs before that function (again, except for the vendor
check) is redundant.

This is not expected to alter any functionality except for the ordering
of messages printed by intel_pstate_init() when it is going to return an
error before attempting to register the driver.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/2776745.mvXUDI8C0e@rjwysocki.net