x86/intel_rdt: Get rid of anon union

gcc-4.4.3 fails to statically initialize members of a anon union.
See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=10676



The storage saving is not really worth it and aside of that it will catch
usage of the cache member for bandwidth and vice versa easier.

Fixes: 05b93417 ("x86/intel_rdt/mba: Add primary support for Memory Bandwidth Allocation (MBA)")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>