powerpc: Option FB_FSL_DIU is not really optional for mpc512x

powerpc: Option FB_FSL_DIU is not really optional for mpc512x

In powerpc randconfig builds, this keeps showing up:

  CC      arch/powerpc/platforms/512x/mpc512x_shared.o
arch/powerpc/platforms/512x/mpc512x_shared.c:70:9: warning: 'enum fsl_diu_monitor_port' declared inside parameter list
arch/powerpc/platforms/512x/mpc512x_shared.c:70:9: warning: its scope is only this definition or declaration, which is probably not what you want
arch/powerpc/platforms/512x/mpc512x_shared.c:69:56: error: parameter 1 ('port') has incomplete type
arch/powerpc/platforms/512x/mpc512x_shared.c:69:5: warning: function declaration isn't a prototype
arch/powerpc/platforms/512x/mpc512x_shared.c:84:9: warning: 'enum fsl_diu_monitor_port' declared inside parameter list
arch/powerpc/platforms/512x/mpc512x_shared.c:83:56: error: parameter 1 ('port') has incomplete type
arch/powerpc/platforms/512x/mpc512x_shared.c:83:6: warning: function declaration isn't a prototype
arch/powerpc/platforms/512x/mpc512x_shared.c:88:36: warning: 'enum fsl_diu_monitor_port' declared inside parameter list
arch/powerpc/platforms/512x/mpc512x_shared.c:88:57: error: parameter 1 ('port') has incomplete type
arch/powerpc/platforms/512x/mpc512x_shared.c:88:6: warning: function declaration isn't a prototype
arch/powerpc/platforms/512x/mpc512x_shared.c:187:54: error: parameter 1 ('port') has incomplete type
arch/powerpc/platforms/512x/mpc512x_shared.c:187:1: error: return type is an incomplete type
arch/powerpc/platforms/512x/mpc512x_shared.c:187:1: warning: function declaration isn't a prototype
arch/powerpc/platforms/512x/mpc512x_shared.c: In function 'mpc512x_valid_monitor_port':
arch/powerpc/platforms/512x/mpc512x_shared.c:189:9: error: 'FSL_DIU_PORT_DVI' undeclared (first use in this function)
arch/powerpc/platforms/512x/mpc512x_shared.c:189:9: note: each undeclared identifier is reported only once for each function it appears in
arch/powerpc/platforms/512x/mpc512x_shared.c:189:2: warning: 'return' with a value, in function returning void
make[2]: *** [arch/powerpc/platforms/512x/mpc512x_shared.o] Error 1

The reason is that mpc512x_shared.c has a couple token #ifdef
on FB_FSL_DIU/FB_FSL_DIU_MODULE, but they don't come close to
masking all the DIU dependencies, as the above fail shows.

Rather than sprinkle more pointless #ifdef in this file, just
remove the existing two, and make FB_FSL_DIU part of the
dependency.  The mpc512x_defconfig already has the line
"CONFIG_FB_FSL_DIU=y" so this change should be zero impact
on real world configs.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>