iommu/sun50i: Constify sun50i_iommu_ops

iommu/sun50i: Constify sun50i_iommu_ops

The struct sun50i_iommu_ops is not modified and can be made const to
allow the compiler to put it in read-only memory.

Before:
   text    data     bss     dec     hex filename
  14358    2501      64   16923    421b drivers/iommu/sun50i-iommu.o

After:
   text    data     bss     dec     hex filename
  14726    2117      64   16907    420b drivers/iommu/sun50i-iommu.o

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20200525214958.30015-3-rikard.falkeborn@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>