uartlite: allow building for timberdale MFD

Some configurations of the Timberdale FPGA has the uartlite
included.

Signed-off-by: Richard Röjfors <richard.rojfors@mocean-labs.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>