ARM: shmobile: r8a7790 SoC 64-bit DT support

The r8a7790 SoC supports LPAE and has memory window up to
0x2ffffffff. Convert to 64-bit addresses by enlarging
#addr-cells and #size-cells to 2.

Signed-off-by: Takashi Yoshii <takashi.yoshii.zj@renesas.com>
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>