ARM: pxa: pxa95x/saarb depends on pxa3xx code

saarb uses pxa3xx_map_io and pxa3xx_handle_irq, which are part
of the pxa3xx code. This makes sure the necessary header and
implementation is used when building the board file.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>