[POWERPC] Don't build arch/powerpc/sysdev/dcr.c for ARCH=ppc kernels
[POWERPC] Don't build arch/powerpc/sysdev/dcr.c for ARCH=ppc kernels

dcr.c is an arch/powerpc only thing.  Compiling ppc405 arch/ppc kernels
throws warnings without this change.

Signed-off-by: Grant Likely <9069e6f5a2b566e2674a0ba1e2bf39c12c195fad@secretlab.ca>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs