powerpc/mpc5200: add options to mpc5200_defconfig

Add the following options to the mpc5200_defconfig, needed
for the a4m072 board support:

CONFIG_AMD_PHY=y
CONFIG_GPIO_SYSFS=y
CONFIG_SENSORS_LM87=m
CONFIG_RTC_DRV_PCF8563=m

Signed-off-by: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <wd@denx.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>