media: venus: core: Add io base variables for each block

New silicon means that the pre-determined offsets we have been using
in this driver no longer hold. Existing blocks of registers can exist at
different offsets relative to the IO base address.

This commit adds a routine to assign the IO base hooks a subsequent commit
will convert from absolute to relative addressing.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>