capsules: ssd1306: fix column command fmt

Setting the upper and lower bits are two separate commands, and there
should be a shift as the upper bits are set in the lower four bits of
the command.

We aren't using this command in the current driver, so I didn't notice
this issue.

capsules/extra/src/ssd1306.rs

@@ -186,7 +186,7 @@ impl Command {
                 1
             }
             Self::SetHigherColumnStartAddress { address } => {
-                buffer[0] = 0x10 | (address & 0xF);
+                buffer[0] = 0x10 | ((address >> 4) & 0xF);
                 1
             }
             Self::SetMemoryAddressingMode { mode } => {