video: da8xx-fb: Fix build warning on unused label

Patch fixes build warning on label "err_cpu_freq" when CONFIG_CPU_FREQ
is not defined.

Signed-off-by: Manjunathappa, Prakash <prakash.pm@ti.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>