KVM/MIPS32: Binary patching of select privileged instructions.

Currently, the following instructions are translated:
- CACHE (indexed)
- CACHE (va based): translated to a SYNCI, overkill on D-CACHE operations,
  but still much faster than a trap.
- mfc0/mtc0: the virtual COP0 registers for the guest are implemented as
  2-D array.
  [COP#][SEL] and this is mapped into the guest kernel address space @ VA 0x0.
  mfc0/mtc0 operations are transformed to load/stores.

Signed-off-by: Sanjay Lal <sanjayl@kymasys.com>
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>