ppc: ppc405: ppc405-generic_flash_defconfig

Remove redundant defconfig file. Boot via flash can be configured via
Kconfig.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Michal Simek <michal.simek@xilinx.com>

configs/xilinx-ppc405-generic_flash_defconfig

-CONFIG_PPC=y
-CONFIG_4xx=y
-CONFIG_TARGET_XILINX_PPC405_GENERIC=y
-CONFIG_SYS_EXTRA_OPTIONS="SYS_TEXT_BASE=0xF7F60000,RESET_VECTOR_ADDRESS=0xF7FFFFFC"
-# CONFIG_CMD_IMLS is not set
-# CONFIG_CMD_SETEXPR is not set
-# CONFIG_CMD_NET is not set
-# CONFIG_CMD_NFS is not set