netlink: eeprom: Fix compilation when pretty dump is disabled

When pretty dump is disabled (i.e., configure --disable-pretty-dump),
the following errors are emitted:

/usr/bin/ld: netlink/module-eeprom.o: in function `decoder_print':
netlink/module-eeprom.c:330: undefined reference to `sff8636_show_all_paged'
netlink/module-eeprom.c:334: undefined reference to `cmis_show_all'
netlink/module-eeprom.c:325: undefined reference to `sff8079_show_all'

The else clause is unreachable when pretty dump is disabled, so wrap it
with ifdef directive.

This will be re-worked in future patches where the netlink code only
queries the SFF-8024 Identifier Value and defers page requests to
individual parsers.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>