tty/synclink: remove leftover bits of non-PCI card support

Since commit 1355cba ("tty/synclink: remove ISA support"), the
synlink driver only supports PCI card.  Remove any leftover dead code
to support other cards.

Signed-off-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Christoph Hellwig