habanalabs: add callback and field to be used for debugfs refactor

This is a preparation for unifying the code of accessing device memory
through debugfs. Add struct fields and callbacks that will later
be used in debugfs code and will reduce code duplication
among the different read{32,64}/write{32,64} callbacks of
every asic.

Signed-off-by: Dafna Hirschfeld <dhirschfeld@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>