Is there any reason an i7-7920HQ wouldn't work with an HM175 chipset?
Sure..some technologies are not supported ( I think vpro wouldn't be)
but the power specifications and the socket are the same as an i7-7700HQ.
In order for a processor to be supported, it must be socket, board and BIOS compatible. The fact that a processor fits in a socket does not mean that the board (through power provisions, etc.) or the board's BIOS will provide support for this processor. Bottom line, you need to talk to the board's manufacturer to determine whether the processor will be supported.
Hope this helps,
That and others, yes. The BIOS support is the biggest hurdle. I have seen cases where, not only is a particular processor not supported, they have used Whitelists to prevent their use even in an unsupported state (it should be obvious that I consider manufacturers who implement Whitelists as being the slimiest of scum).
Final answer: Contact your board manufacturer and ask them about BIOS compatibility,