[HVX] Fix state_var issue

[rootjalex]

The issue in #6893 is the result of an attempt to dereference a pointer to the module_state pointer. This PR simply adds a runtime method to dereference the pointer, in order to fix that issue. I'm not necessarily sure if this is the best approach, would love feedback from anyone who knows the HVX runtime better than I do.

[abadams]

@pranavb-ca might be able to weigh in

[pranavb-ca]

LGTM. @aankit-ca can help you test this if you need. (sorry, i am on vacation with limited access to my work machine).

[rootjalex]

Thanks for taking a look @pranavb-ca - sorry for bothering you on your vacation!

[steven-johnson]

So how confident are we in this change? Do we have a way to verify that the null-check code is actually being exercised?

[rootjalex]

I don't think we have a way to verify that it is, however this change is actually safer - the current version in main will just load without the nullptr check.

[rootjalex]

@aankit-ca Any chance you could look at this? #6884 is stalled until this PR goes through

[steven-johnson]

Monday review ping to @aankit-ca

[rootjalex]

bump

[steven-johnson]

If @aankit-ca isn't available for this review, we should either find someone else or just land it as-is.