x86: Move SSDT table to a writer function

Move this table over to use a writer function, moving the code from the
x86 implementation.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/acpi/Makefile b/lib/acpi/Makefile
index ccdf428..552d499 100644
--- a/lib/acpi/Makefile
+++ b/lib/acpi/Makefile
@@ -17,4 +17,5 @@
 endif
 
 obj-y += facs.o
+obj-y += ssdt.o
 endif