D81 formatting fails

[rhester72]

Testing was performed on commit 7b4d77fb5ac05aca6c2428ad772017976d88951a

When attempting to format a d81/1581 image, formatting never complates. Steps to reproduce:

• Mount d81 disk image in drive 8
• Issue the command:

HEADER"MYDISK",IMD

• Respond to the "ARE YOU SURE?" prompt with Y

The format attempt will never return. This does not occur with g71/1571.

[eriks5]

This is an upstream issue. Formatting with the 1581 is not supported by the C64 core either. The write track functionality is not implemented: https://github.com/MiSTer-devel/C64_MiSTer/blob/master/rtl/iec_drive/fdc1772.v#L657

[eriks5]

Tagged wrong issue