iommu/ipmmu-vmsa: Clarify supported platforms

The Renesas IPMMU-VMSA driver supports not just R-Car H2 and M2 SoCs,
but also other R-Car Gen2 and R-Car Gen3 SoCs.

Drop a superfluous "Renesas" while at it.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Joerg Roedel <jroedel@suse.de>