target-arm: implement LDA/STL instructions

This adds support for the ARMv8 load acquire/store release instructions.
Since qemu does nothing special for memory barriers, these can be
emulated like their non-acquire/release counterparts.

Signed-off-by: Mans Rullgard <mans@mansr.com>
target-arm: explicitly decode SEVL instruction

The ARMv8 SEVL instruction is in the architectural hint space already
emulated as nop.  This makes the decoding of SEVL explicit for clarity.

Signed-off-by: Mans Rullgard <mans@mansr.com>
target-arm: handle armv8 vsel instructions

Signed-off-by: Mans Rullgard <mans@mansr.com>
target-arm: handle vmaxnm/vminnm instructions

Signed-off-by: Mans Rullgard <mans@mansr.com>