Rework "Update more link-layer dissectors to void functions"

Rework "Update more link-layer dissectors to void functions"

It's a follow-up to commit 81dbf4a0b05092760d0ff0cdd48c692e4769ba99.

There is no need to update ether_print(), ether_common_print() and
ether_switch_tag_print() to void functions: back to u_int functions.

There is also no need to add a flag parameter to ether_print(),
ether_common_print() and ether_switch_tag_print(): Remove it.