powerpc: DM_SPI, DM_ETH, Remove some platforms Add DM_SPI, DM_SPI_FLASH support for powerpc platforms Add DM_ETH support on P1010RDB, P1020RDB, P2020RDB reduce number of WATCHDOG_RESET calls from flush_cache Remove some un-maintained powerpc platforms Add USB_STORAGE support in config Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>