Split common board code for R-Car Gen3 and Gen4 into separate files.
The R-Car Gen3 board code contains fixups specific to TFA which are
no longer required on R-Car Gen4, keep those fixups in its own file
so they would not interfere with Gen4.
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
All R-Car Gen4 board files are copies of one another at this point.
Deduplicate them into single board/renesas/rcar-common/gen4-common.c
and remove all the duplicates. The one exception is R-Car V3U Falcon
board, which enables RWDT reset in board_init(), conditionally build
RWDT enablement in board_init() in the new common code for V3U.
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>