ucode: enable ucode-mod-zlib

ucode: enable ucode-mod-zlib

The module exists in ucode and has been present for a while
but has not been enabled. It provides the ucode zlib module
for handling gzip and zlib compression in ucode scripts.

The package is ~ 5Kb. Installed ~18Kb.

Signed-off-by: Paul Donald <newtwen+github@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21417
Signed-off-by: Robert Marko <robimarko@gmail.com>
(cherry picked from commit 16ae5c23e59555eb61100a8a5524ed5b3c6c49a7)
Link: https://github.com/openwrt/openwrt/pull/21608
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>