wifi: iwlwifi: uninitialized variable in iwl_acpi_get_ppag_table()

This is an error path and Smatch complains that "tbl_rev" is uninitialized
on this path.  All the other functions follow this same patter where they
set the error code and goto out_free so that's probably what was intended
here as well.

Fixes: e8e10a37

 ("iwlwifi: acpi: move ppag code from mvm to fw/acpi")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://msgid.link/09900c01-6540-4a32-9451-563da0029cb6@moroto.mountain
Signed-off-by: Johannes Berg <johannes.berg@intel.com>