powerpc/52xx: fix build breakage for MPC5200 LPBFIFO module

The MPC5200 LPBFIFO driver requires the bestcomm module to be
enabled, otherwise building will fail. Fix it.

Cc: <stable@vger.kernel.org> # 3.10+
Reported-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>