Describe the bug
Monotonic clock initialization relies on cpuinfo's model name field. However, this is not guaranteed to work especially on AMD CPUs because the model name does not contain the clock speed.

To reproduce

1. Build with CFLAGS="-DUSE_PROCESSOR_CLOCK"
2. Run valkey-server
3. Error message printed: "monotonic: x86 linux, unable to determine clock rate"

Expected behavior
Monotonic clock initialization should work without errors regardless of which CPU being used.