km/scripts: load fdt_bid_kwkey.dtb when working with tftp

When loading the dtb file via tftp we should load the one which matches
boardId and hwKey and not a common one for the boardname. We have boards
were different hwKeys are used and then we may load an incorrect dtb
file. If no fdt_bid_kwkey.dtb file is not a fallback to boardname.dtb is used.
Signed-off-by: NHolger Brunck <holger.brunck@keymile.com>
Signed-off-by: NTobias Müller <Tobias.Mueller@keymile.com>
Signed-off-by: NValentin Longchamp <valentin.longchamp@keymile.com>
Reviewed-by: NHeiko Schocher <hs@denx.de>

board/keymile/scripts/develop-common.txt

@@ -3,7 +3,7 @@ bootcmd=run ${subbootcmds}
 configure=run set_uimage; km_setboardid && saveenv && reset
 subbootcmds=tftpfdt tftpkernel nfsargs add_default boot
 nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${toolchain}/${arch}
-tftpfdt=if run set_fdthigh || test ${arch} != arm; then tftpboot ${fdt_addr_r} ${hostname}/${hostname}.dtb; else true; fi
+tftpfdt=if run set_fdthigh || test ${arch} != arm; then if tftpboot ${fdt_addr_r} ${hostname}/fdt_0x${IVM_BoardId}_0x${IVM_HWKey}.dtb; then; else tftpboot ${fdt_addr_r} ${hostname}/${hostname}.dtb; fi; else true; fi
 tftpkernel=tftpboot ${load_addr_r} ${hostname}/${uimage}
 toolchain=/opt/eldk
 rootfssize=0