usb: dwc3-msm: Set proper ssphy flag during peripheral bus suspend

'Commit fb34a13a ("usb: dwc3: Add support for 4 PHYs for dual
port controller")' updated the SSPHY flags with DEVICE_IN_SS_MODE
bit in dwc3_msm_is_host_superspeed function. This was moved from
dwc3_msm_suspend function but flag update for device mode was not
taken care of. This leads to improper fields in the
AUTONOMOUS_MODE_CTRL register and SSPHY irq gets fired as soon as
we go into low power mode and enable the ss_phy_irq.
Fix this by updating the ssphy flags with DEVICE_IN_SS_MODE bit
based on speed in dwc3_msm_is_dev_superspeed function.

Change-Id: Ie669ff2ae80b87ace624cfcefeefb34b8a4cc0a0
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>