hwvdf: Allow setting max frequency when in auto adjustment mode

[cmmarslender]

Allows setting a max frequency when in the auto adjusting mode

With Option Set:

./hw_vdf_client --freq 1100 --auto-freq-period 10 --max-freq 1110 [...]
2023-11-22T01:33:03.998 Setting frequency to 1100.000000 MHz
2023-11-22T01:33:04.114 Frequency is 1100.000000 MHz
[...]
2023-11-22T01:33:14.117 Frequency is increased to 1110.0 MHz; freq_idx = 7635
2023-11-22T01:33:24.117 Can't increase frequency, already at maximum
2023-11-22T01:33:34.117 Can't increase frequency, already at maximum

Without Option Set:

./hw_vdf_client --freq 1100 --auto-freq-period 10 [...]
2023-11-22T01:35:11.408 Setting frequency to 1100.000000 MHz
2023-11-22T01:35:11.524 Frequency is 1100.000000 MHz
[...]
2023-11-22T01:35:21.527 Frequency is increased to 1110.0 MHz; freq_idx = 7635
2023-11-22T01:35:31.531 Frequency is increased to 1111.1 MHz; freq_idx = 7636
2023-11-22T01:35:41.534 Frequency is increased to 1112.5 MHz; freq_idx = 7637
2023-11-22T01:35:51.537 Frequency is increased to 1114.2 MHz; freq_idx = 7638

[wjblanke]

aok