sign_rpm.bbclass: ignore thread count
From: Daniel McGregor <daniel.mcgregor@vecima.com>
Similar to sign_ipk, ignore the number of threads used for signing
RPMs.
Signed-off-by: Daniel McGregor <daniel.mcgregor@vecima.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>