85xx: Fix compile breakage with MPC8540EVAL

Configuring for MPC8540EVAL board...
mpc8540eval.c: In function 'checkboard':
mpc8540eval.c:53: error: invalid operands to binary /
make[1]: *** [mpc8540eval.o] Error 1

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>