add back missing dependencies in SkColorPriv.h

SkColorPriv.h depends on SkColor.h and SK_RGBA_x32_SHIFT

TBR=reed@google.com
Bug: skia: 6898
Change-Id: I3f7bbaff306298e89bfb0bb571b19d6d223147e5
Reviewed-on: https://skia-review.googlesource.com/47861
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
2 files changed