arm64: FIQs are unused

So any FIQ handling is superfluous at the moment.  The functions to
disable/enable FIQs is kept around if ever someone needs them in the
future, but existing calling sites including arch_cpu_idle_prepare()
may go for now.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: f864b61ee49bbf3faf9a10b9770c719536328d01
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[imaund@codeaurora.org: Resolve the context conflict with the new call to
  flush_cache_all]
Signed-off-by: Ian Maund <imaund@codeaurora.org>