i2c-highlander: remover superflous variable

When cppcheck found this flaw

[./i2c/busses/i2c-highlander.c:284]: (style) Warning - using char variable in bit operation

it was noted that the 'read'-variable could be simply removed as read_write can
only be 0 or 1 anyhow. So, we remove the flaw and simplify the code.

Reported-by: d binderman <dcb314@hotmail.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Jean Delvare <khali@linux-fr.org>
Cc: Ben Dooks <ben-linux@fluff.org>