[ARM] 4663/1: Only putc uncompressor output into FFUART if it was enabled by the bootloader

Also, use existing register and bit definitions instead of numbers.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>