atmel_serial: fix bugs in probe() error path and remove()

When an error happens in probe(), the clocks should be disabled, but
only if the port isn't already used as a console.

In remove(), the port struct shouldn't be freed because it's defined
statically.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Tested-by: Marc Pignat <marc.pignat@hevs.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>