target-arm: Fix "no 64-bit EL2" assumption in arm_excp_unmasked()

target-arm: Fix "no 64-bit EL2" assumption in arm_excp_unmasked()

The code in arm_excp_unmasked() suppresses the ability of PSTATE.AIF
to mask exceptions from a lower EL targeting EL2 or EL3 if the
CPU is 64-bit. This is correct for a target of EL3, but not correct
for targeting EL2. Further, we go to some effort to calculate
scr and hcr values which are not used at all for the 64-bit CPU
case.

Rearrange the code to correctly implement the 64-bit CPU logic
and keep the hcr/scr calculations in the 32-bit CPU codepath.

Signed-off-by: Peter Maydell <[email protected]>
Message-id: 1444327729[email protected]
Reviewed-by: Edgar E. Iglesias <[email protected]>
Tested-by: Edgar E. Iglesias <[email protected]>