TCPMv2:Correct get_usb4_cable_speed() function
TCPMv2:Correct get_usb4_cable_speed() function

If a passive USB3gen2 cable NAKs to the discover SVID/mode query, we
need to enter USB4 with USB3gen2 passive cable.

When a cable NAKs to discover query, the port limits it's Thunderbolt
speed to Passive Gen 2 cable speed. So, this CL modifies the
get_usb4_cable_speed() function, to obtain the thunderbolt speed from
get_tbt_cable_speed() instead of board_get_max_tbt_speed() function

BUG=b:168060760
BRANCH=None
TEST=Checked on volteer, able to enumerate the USB3Gen2 cables that NAKs
     to discover SVID query.

Signed-off-by: Ayushee <5730d7ed61dc96fa04bcc2bc2e4ce32af5b2c19d@intel.com>
Change-Id: Id38ca12bb695ed256098d66b098aafa1bc75aed9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2404604
Reviewed-by: Vijay P Hiremath <006c712879a3af08bfdb5c2b8491a8b2d5fd73cd@intel.com>
Reviewed-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec