usb: dwc2: drd: reset current session before setting the new one

If role is changed without the "none" step, A- and B- valid session could
be set at the same time. It is an issue.
This patch resets A-session if role switch sets B-session, and resets
B-session if role switch sets A-session.
Then, it is possible to change the role without the "none" step.

Fixes: 17f93402

 ("usb: dwc2: override PHY input signals with usb role switch support")
Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20211005095305.66397-4-amelie.delaunay@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>