ARM: dts: uniphier: move aliases node up to satisfy fdtgrep

Currently, fdtgrep would not accept uniphier-ph1-ld20-ref.dtb
and uniphier-ph1-ld11-ref.dtb unless the aliases node comes
the first in the root node.

$ make -s uniphier_pxs2_ld6b_defconfig
$ make CROSS_COMPILE=arm-linux-gnueabi- DEVICE_TREE=uniphier-ph1-ld20-ref
  [snip]
  LDS     spl/u-boot-spl.lds
  LD      spl/u-boot-spl
  OBJCOPY spl/u-boot-spl-nodtb.bin
  FDTGREP spl/u-boot-spl.dtb
Error at 'fdt_find_regions': FDT_ERR_BADLAYOUT
/aliases node must come before all other nodes
Error: FDT_ERR_BADMAGIC
make[1]: *** [spl/u-boot-spl.dtb] Error 1
make: *** [spl/u-boot-spl] Error 2

This commit moves the aliases node as the error message from the
fdtgrep tool suggests, although this requirement does not sound
reasonable to me.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>