read_gpioab()/write_gpioab() aren't congruent

[AGSaidi]

Thanks for great and straightforward library to interface with the mcp23017.

I came across a bug when using read_gpioab() and write_gpioab(). The read half returns GPIOA in bits 8:15 while the write version expects GPIOA in the low bits 0:7. The write version make more sense to me and the change is simply:

 --- lib.rs.old	2022-01-09 13:04:33.000000000 -0600
+++ lib.rs	2022-01-09 13:04:25.000000000 -0600
@@ -148,7 +148,7 @@
     /// Reads all 16 pins (port A and B) into a single 16 bit variable.
     pub fn read_gpioab(&mut self) -> Result<u16, E> {
         let buffer = self.read_double_register(Register::GPIOA)?;
-        Ok((buffer[0] as u16) << 8 | (buffer[1] as u16))
+        Ok((buffer[1] as u16) << 8 | (buffer[0] as u16))
     }

     /// Reads a single port, A or B, and returns its current 8 bit value.

However, if someone was relying on it, it would be a breaking change.