board: hoperun: Switch to use complete DTS files from upstream DTS

board: hoperun: Switch to use complete DTS files from upstream DTS

For upstream Linux kernel we use below DTBs for HiHope boards:
- r8a774a1-hihope-rzg2m-ex.dtb
- r8a774e1-hihope-rzg2h-ex.dtb
- r8a774b1-hihope-rzg2n-ex.dtb

Update the CONFIG_OF_LIST to match the above. Now that we have switched
upstream DTS, drop deleting the nodes and also rename the
r8a774*-u-boot.dtsi files to r8a774*-ex-u-boot.dtsi to match the OF_LIST
files so that the `bootph-all` property gets applied to required nodes
in upstream DTS.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Chris Paterson <chris.paterson2@renesas.com>