Cleaning up the svd2rust deck.

[jonathanpallant]

Revised the svd2rust deck.

• Talk about bitfields to avoid confusion with fields in structs
• Update link to nrf52840 PAC
• Show ZST alternative
• Note that some RISC-V chips have SVD files

[miguelraz]

I left two notes to explain acronyms that I wasn't familiar with and that I didn't see defined earlier in the slide. Feel free to drop them if you don't think they are necessary.

[jonathanpallant]

Add definition of UART and UARTE in the notes.

[jonathanpallant]

Thanks!