[SYCL][Matrix] Add W/A for several corner cases of AccessChain usage

[MrSidims]

These corner cases are:

1. AccessChain uses are optimized out of LLVM IR modules, leaving the call unused;
2. AccessChain result is used in GEP 0,0 instruction for bfloat16 (instead of the immidiate use by load or store).

All of these issues are or will be fixed in our drivers, but since the cadence of the driver update is relatively big the W/A is added in the frontend for an immediate fix.

[MrSidims]

LGTM, just a few nits and one question: should we open an issue to remind us to remove this W/A when possible?

Sure, I can open it. But first I need to create a tracker to say, that the issue exists in the first place...

[MrSidims]

LGTM, just a few nits and one question: should we open an issue to remind us to remove this W/A when possible?

I've created an internal tracker for this.

[MrSidims]

@intel/llvm-gatekeepers please help with the merge

[sarnex]

No idea, probably some issue on Github's end, I'll keep trying.

[sarnex]

Still stuck, hopefully it fixes itself lol

[sarnex]

we did it