drivers/video/ep93xx-fb.c: clean up error-handling code

There were two problems in this code: failure of the setup function should
free locally allocated resources like other nearby failures, and the test
if (&info->cmap) can never be false.  To generally clean things up, this
patch reorders the error handling code at the failed label and adds labels
so that the conditionals are not necessary.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>