usb: typec: tcpci: Add support when hidden tx registers are inaccessible

TCPCI spec forbids direct access of TX_BUF_BYTE_x register.
The existing version of tcpci driver assumes that those registers
are directly addressible. Add support for tcpci chips which do
not support direct access to TX_BUF_BYTE_x registers. TX_BUF_BYTE_x
can only be accessed by I2C_WRITE_BYTE_COUNT.

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Link: https://lore.kernel.org/r/20200901025927.3596190-3-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>