ARM: pxa: Add standard UART to hx4700_pin_config[]

Add the two standard UART signals (GPIO46_STUART_RXD, GPIO47_STUART_TXD) to the
initial mfp config table hx4700_pin_config[] passed to pxa2xx_mfp_config().
Although pxa2xx_transceiver_mode() can subsequently set these two signals via
its own call to pxa2xx_mfp_config(), pxa2xx_transceiver_mode() is only present
when CONFIG_PXA_FICP=y. Hence this patch provides a default mfp config.

Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>