Fix code to allow usage of -Wall in libpayload and the sample (trivial).

Fix code to allow usage of -Wall in libpayload and the sample (trivial).

This even fixes two bugs:

 - get_cpu_speed() didn't return a value.

 - The line
     win->_color - PAIR_NUMBER(0);
   should actually be
     win->_color = PAIR_NUMBER(0);

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3182 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1