arm64: kvm: use inner-shareable barriers for inner-shareable maintenance

arm64: kvm: use inner-shareable barriers for inner-shareable maintenance

In order to ensure completion of inner-shareable maintenance instructions
(cache and TLB) on AArch64, we can use the -ish suffix to the dsb
instruction.

This patch relaxes our dsb sy instructions to dsb ish where possible.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit ee9e101c11478680d579bd20bb38a4d3e2514fe3)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>