acpi: support 64bit in acpi_find_table for DSDT and FACS

Use X_DSDT and X_FIRMWARE_CTRL if available.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Rebased on -next to use nomap:
Signed-off-by: Simon Glass <sjg@chromium.org>