If acpi=force is passed on the command line, it forces ACPI to be
the only available boot method, hence it must be left enabled even
if the initialization and sanity checks on ACPI tables fails.

This patch refactors ACPI initialization to prevent disabling ACPI
if acpi=force is passed on the command line.
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: NHanjun Guo <hanjun.guo@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>