i2c: cros_ec: Remove EC_I2C_FLAG_10BIT

In <https://lkml.org/lkml/2014/6/10/265> pointed out that the 10-bit
flag in the cros_ec_tunnel was useless.  It went into a 16-bit flags
field but was defined at (1 << 16).

Since we have no 10-bit i2c devices on the other side of the tunnel on
any known devices this was never a problem.  Until we do it makes
sense to remove this code.  On the EC side the code to handle this
flag was removed in <https://chromium-review.googlesource.com/204162>.

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>