Adapt build instructions to new keyboard name

keyboards/ergodox_infinity/readme.md

@@ -3,21 +3,21 @@
 The Infinity is two completely independent keyboards, and needs to be flashed
 for the left and right halves seperately.  To flash them:
 
-  - Build the firmware with `make infinity-keymapname`
+  - Build the firmware with `make ergodox_infinity-keymapname`
 
   - Plug in the left hand keyboard only.
 
   - Press the program button (back of keyboard, above thumb pad).
 
-  - Install the firmware with `sudo make infinity-keymapname-dfu-util`
+  - Install the firmware with `sudo make ergodox_infinity-keymapname-dfu-util`
 
-  - Build right hand firmware with `make infinity-keymapname MASTER=right`
+  - Build right hand firmware with `make ergodox_infinity-keymapname MASTER=right`
 
   - Plug in the right hand keyboard only.
 
   - Press the program button (back of keyboard, above thumb pad).
 
-  - Install the firmware with `sudo make infinity-keymapname-dfu-util MASTER=right`
+  - Install the firmware with `sudo make ergodox_infinity-keymapname-dfu-util MASTER=right`
 
 More information on the Infinity firmware is available in the [TMK/chibios for
 Input Club Infinity Ergodox](https://github.com/fredizzimo/infinity_ergodox/blob/master/README.md)
@@ -42,4 +42,4 @@ You have a few options in how you flash the firmware:
 
 - For minor changes such as changing only the keymap without having updated
   any part of the firmware code itself, you can program only the MASTER half.
-  It is safest to program both halves though.
+  It is safest to program both halves though.