Rely on external library for reversing bits

[RandomInsano]

I was just perusing the codebase here and thought I'd mention you can use bit_reverse instead of rolling your own. Specifically this guy.

The only benefit here would be to save some space if multiple people are using the same crate / version. Other option is that we request it be included in the HAL's SPI layer because I hit the same problem building a driver for a PlayStation controller where my target doesn't have hardware support for flipping the bits for me.

[peter9477]

Note that Rust (as of 1.37.0) may have support for intrinsics such as u8::reverse_bits(), at least on supporting micros (not including Cortex-M0 or M33 but including M4, M7 and others). I have not tried actually using those yet but if it can do it with a single RBIT instruction instead of a function and table of 256 bytes, that's a big win.