AmpereAltraPkg/AmpereCpuLib: Retrieve correct CPU clock speed

Ampere Altra Family has no concept about turbo frequency. The platform
hand-off block (HOB) does not have that information and the default value
is zero. Hence, this patch removes the check of turbo capability, and
always get CPU max clock speed from HOB.

Signed-off-by: Chuong Tran <chuong@os.amperecomputing.com>