package/zlib: zlib-ng only available on some archs

Upstream has code only for those architectures, with no fallback
generic code, so we must restrict zlib-ng to only those four archs...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Nicolas Cavallari <Nicolas.Cavallari@green-communications.fr>
Cc: Adam Duskett <aduskett@gmail.com>
Cc: Stefan Fröberg <stefan.froberg@petroprogram.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
[Thomas: fix typoes in the Config.in option name.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>