board::t41() does not expose SAI.

[fitzthum]

Maybe I am missing something, but I can't figure out how to access the SAI driver. I see that there are SAI instances in board::instances, but board::t41() doesn't return them.

How can I get access to the SAI instance to construct a SAI driver via imxrt-hal::sai? If I try to use SAI instances from board::instances() directly, I run into issues with the borrow checker.

[mciantyre]

This might need BSP changes. If you'd like to contribute, I'm happy to publish a release.

Changes that expose a new peripheral through the BSP tend to be backwards compatible. Here's some examples.

• Add BSP Support for FlexCAN(1/2) #162
• Add FlexIO registers to Resources object #140
• Added lpuart5 and lpuart7 #170

[tacertain]

Submitted PR #184