acpi/acpigen_dptf: Add pkg return to dptf_write_power_limits()

The PPCC method should return the package, but is missing the return
statement, leading to DPTF/S0ix to not function properly. Add the
required return statement.

TEST=build/boot Win11 on google/banshee, verify DPTF, S0ix functional.

Change-Id: I051db7d69dd6cdfbb07caf649247ee166c1c74ac
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72921
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Tim Wawrzynczak <inforichland@gmail.com>
Reviewed-by: Felix Singer <felixsinger@posteo.net>

src/acpi/acpigen_dptf.c

@@ -400,6 +400,8 @@ void dptf_write_power_limits(const struct dptf_power_limits *limits)
 	dptf_write_scope(DPTF_CPU);
 	acpigen_write_method("PPCC", 0);
 
+	acpigen_emit_byte(RETURN_OP);
+
 	pkg_count = acpigen_write_package(1); /* 1 for the Revision */
 	acpigen_write_integer(PPCC_REVISION); /* revision */