usb: phy: snps: Enable auto resume feature only in host mode

'Commit f62b4c27 ("usb: phy: snps: Enable auto-resume during
host mode bus suspend")' started enabling USB auto resume for
peripheral mode bus suspend as well. If the auto resume feature
is enabled in device mode, the device is unable to detect the
resume signalling by the host in some cases. And the auto resume
feature is applicable only in host mode.
So, enable the auto resume feature only in host mode.

Change-Id: I59155bc122ac4f5c9bb04cb4ff487c7a6ba89e47
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>