cpufreq: amd-pstate: Remove amd_get_{min,max,nominal,lowest_nonlinear}_freq()

cpufreq: amd-pstate: Remove amd_get_{min,max,nominal,lowest_nonlinear}_freq()

amd_get_{min,max,nominal,lowest_nonlinear}_freq() functions merely
return cpudata->{min,max,nominal,lowest_nonlinear}_freq values.

There is no loss in readability in replacing their invocations by
accesses to the corresponding members of cpudata.

Do so and remove these helper functions.

Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Li Meng <li.meng@amd.com>
Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>