FREEZER: Set 40 MHz mode correctly

[dansanderson]

freezer.c on the development branch is setting 40 MHz mode incorrectly: both FAST and VFAST must be set.

Demonstration:

10 T=TI:FOR I=0 TO 1000:NEXT:PRINT TI-T

From the boot state, run this. Then open the Freezer, press F, then press F3 to resume, and run the program again. Repeat for all five of 40 MHz, 1 MHz, 2 MHz, 3 MHz, then 40 MHz again. Results:

1. Boot state: ~0.03 (40 MHz)
2. 1 MHz: ~1.24
3. 2 MHz: ~0.58
4. 3.5 MHz: ~0.29
5. Last run, should be 40 MHz but is actually: ~1.24 (1 MHz)

For full discussion: MEGA65/mega65-rom-public#89