iommu/ipmmu-vmsa: Move num_utlbs to SoC-specific features

The maximum number of micro-TLBs per IPMMU instance is not fixed, but
depends on the SoC type.  Hence move it from struct ipmmu_vmsa_device to
struct ipmmu_features, and set up the correct value for both R-Car Gen2
and Gen3 SoCs.

Note that currently no code uses this value.

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>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>