target-arm: Add AArch64 CPTR registers

target-arm: Add AArch64 CPTR registers

Adds CPTR_EL2/3 system registers definitions and access function.

Signed-off-by: Greg Bellows <greg.bellows@linaro.org>
[PMM: merge CPTR_EL2 and HCPTR definitions into a single
 def using STATE_BOTH;
 don't use readfn/writefn to implement RAZ/WI registers;
 don't use accessfn for the no-EL2 CPTR_EL2;
 fix cpacr_access logic to catch EL2 accesses to CPACR being
 trapped to EL3;
 use new CP_ACCESS_TRAP_EL[23] rather than setting
 exception.target_el directly]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>