iommu/riscv: Include the dword number in RISCV_IOMMU_CMD macros

The command queue entry format is 128 bits. Follow the pattern of the
other drivers and encode the 64 bit dword number in the macro
itself. RISC-V further has similarly named macros that are not field
layout macros, but field content macros which won't get a new number.

Overall this is clearer to understand the code and check for errors like
using the wrong macro in the wrong spot.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Tested-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>