libpayload: Make keycode constants available outside of curses.h.

And include the new, split out version in drivers/keyboard.c and
drivers/usb/usbhid.c. Those files were including curses.h just for those
definitions, but the include path was only fixed up to to point to the
libpayload versions of those files if one of the variants of curses was
compiled in. If neither was, gcc would fall back to the system version of that
header which is wrong.

Change-Id: I8c2ee0baf5f0702bd8c713c8dd4613a4bb269ce5
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: http://review.coreboot.org/2762
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

payloads/libpayload/drivers/keyboard.c

@@ -27,9 +27,9 @@
  * SUCH DAMAGE.
  */
 
+#include <keycodes.h>
 #include <libpayload-config.h>
 #include <libpayload.h>
-#include <curses.h>
 
 #define I8042_CMD_READ_MODE  0x20
 #define I8042_CMD_WRITE_MODE 0x60