target/arm: Implement AArch32 HCR and HCR2

target/arm: Implement AArch32 HCR and HCR2

The AArch32 HCR and HCR2 registers alias HCR_EL2
bits [31:0] and [63:32]; implement them.

Since HCR2 exists in ARMv8 but not ARMv7, we need new
regdef arrays for "we have EL3, not EL2, we're ARMv8"
and "we have EL2, we're ARMv8" to hold the definitions.

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Reviewed-by: Edgar E. Iglesias <[email protected]>
Reviewed-by: Luc Michel <[email protected]>
Message-id: 20180820153020[email protected]