ppc4xx/fdt/flash: Change fdt_fixup_nor_flash_node() to not rely on cs size

This patch changes the behaviour of the fdt_fixup_nor_flash_node()
function. Now it doesn't patch the size of the "reg" property with the
chip-select size, but with the size returned from the new function
flash_get_bank_size(). This function will return per weak default the
flash size of the bank (bank = chip-select numer) detected by the flash
driver. If this does not fit your needs, this function may be overridden
by a board specific one.

For this the parameters needed to be changed. So I intentionally squashed
the PPC4xx stuff using this routine into this patch. Otherwise it would
not be git-bisectable anymore.

The board specific function for the AMCC/APM Ebony eval board is now
included in this patch version.

Signed-off-by: Stefan Roese <sr@denx.de>
Tested-by: Detlev Zundel <dzu@denx.de>
Cc: Gerald Van Baren <vanbaren@cideas.com>
Cc: Wolfgang Denk <wd@denx.de>