lynxpoint: fix mem corruption during ssdt2 gen

The ssdt2 generation code was calling acpigen_patch_len().
However, none of the entries had AML object lengths that
needed patching. That resulted in the following message:

ASSERTION FAILED: file 'src/arch/x86/boot/acpigen.c',  line 52

Additionally, this caused an errant write to a memory address
whose value was in the variable ltop. This was the 0 address.

Change-Id: I44abf5a4e4225220575aee6b5c9bb6b0be093a28
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/56299
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/4182
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/southbridge/intel/lynxpoint/acpi.c

@@ -88,7 +88,6 @@ void acpi_create_serialio_ssdt(acpi_header_t *ssdt)
 	/* Fill the SSDT with an entry for each SerialIO device */
 	for (id = 0; id < 8; id++)
 		len += acpi_create_serialio_ssdt_entry(id, gnvs);
-	acpigen_patch_len(len-1);
 
 	/* (Re)calculate length and checksum. */
 	current = (unsigned long)acpigen_get_current();