Fix compatible string for R-Car Gen4.

Fixes: ae684caf ("iommu/ipmmu-vmsa: Add support for R-Car Gen4")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20220617010107.3229784-1-yoshihiro.shimoda.uh@renesas.comSigned-off-by: Joerg Roedel <jroedel@suse.de>