powerpc/mpc5200: update mpc5200_defconfig to fit for charon board

Add following options to mpc5200_defconfig:

- CONFIG_MTD_PLATRAM=y
  (selects CONFIG_MTD_RAM, so this is removed)
- CONFIG_FIXED_PHY=y
- CONFIG_SENSORS_LM80=y
- CONFIG_FB_FOREIGN_ENDIAN=y
- CONFIG_FB_SM501=m
- CONFIG_RTC_DRV_DS1374=y

Signed-off-by: Heiko Schocher <hs@denx.de>
cc: Grant Likely <grant.likely@secretlab.ca>
cc: Wolfgang Denk <wd@denx.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>