thunderbolt: Rename EEPROM handling bits to match USB4 spec

The structure `tb_eeprom_ctl` is used to show the bits accessed when
reading/writing EEPROM.

As this structure is specified in the USB4 spec as `VSC_CS_4` update
the names and use of members to match the specification. This should not
change anything functionally.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>