zabbix: fix recursive depedency warning on build

zabbix: fix recursive depedency warning on build

The error in the #24828 patch series left Kconfig recursive depedency
error on zabbix-frontend-server. We fix this by update the database
depedencies on zabbix-frontend-server. Now, you must select the PHP8
database module you want _before_ zabbix-frontend-server will be
visible in menuconfig.

This is not a big problem, because zabbix-frontend-server already
depends on having php8 slected before the frontend can be built.

Closes: #28458
Signed-off-by: Daniel F. Dickinson <redacted>