habanalabs: report correct dram size in info ioctl

In case MMU is enabled, we must take MMU page size into
consideration when reporting dram size to the user.
This is because the MMU page size can be a value which is NOT
a power-of-2 value. As a result, the total DRAM size (which is always
a power-of-2 value) needed to be rounded-down.

Signed-off-by: Ofir Bitton <obitton@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>