xen: arm64: asm: remove redundant "cc" clobbers

xen: arm64: asm: remove redundant "cc" clobbers

This resyncs atomics and cmpxchgs with Linux v3.14-rc7 by importing:
commit 95c4189689f92fba7ecf9097173404d4928c6e9b
Author: Will Deacon <will.deacon@arm.com>
Date:   Tue Feb 4 12:29:13 2014 +0000

    arm64: asm: remove redundant "cc" clobbers

    cbnz/tbnz don't update the condition flags, so remove the "cc" clobbers
    from inline asm blocks that only use these instructions to implement
    conditional branches.

    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Tim Deegan <tim@xen.org>