The current reset logic does not always properly reset the device.  For
example, in the case when the perst_b signal is already de-asserted in the
bootloader, the current reset logic fails to trigger a proper assert ->
de-assert reset sequence.

Fix the issue by always triggering the proper reset sequence.

Also explicitly select the desired reset source, i.e., perst_b, and reduce
the wait time after the device comes out of reset from 250 ms to 100 ms,
based on recommendation from the ASIC team.
Tested-by: NVladimir Dreizin <vdreizin@broadcom.com>
Tested-by: NDarren Edamura <dedamura@broadcom.com>
Signed-off-by: NRay Jui <rjui@broadcom.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NVladimir Dreizin <vdreizin@broadcom.com>
Reviewed-by: NTrac Hoang <trhoang@broadcom.com>
Reviewed-by: NScott Branden <sbranden@broadcom.com>