Revert "serial: core: Fix missing shutdown and startup for serial base port"

This reverts commit 83290f9f which is
commit 1aa4ad4e upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Ie0ce689dd59725486dd80d7a5da4d72b5832ad79
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>