acpi: Fix an infinite loop in acpi_table_add

Commit d729bb9a7700e364b1c5f9893d61f07a9e002bce has a typo, causing an
infinite loop in acpi_table_add.

Signed-off-by: Vincent Minet <vincent@vincent-minet.net>
Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
