x86: tangier: acpi: Create buffers outside of the methods

Create buffers outside of the methods as ACPICA 20200214 complains about this:

	Remark 2173 - Creation of named objects within a method is
	highly inefficient, use globals or method local variables
	instead

Reported-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>