claw: rename READ/WRITE defines to avoid redefinitions

READ/WRITE seems to be a bit too generic for defines in a device driver.
Just rename them to READ_CHANNEL/WRITE_CHANNEL which should suffice.

Fixes this:

In file included from drivers/s390/net/claw.c:93:
drivers/s390/net/claw.h:78:1: warning: "WRITE" redefined
In file included from /home2/heicarst/linux-2.6/arch/s390/include/asm/debug.h:12,
                 from drivers/s390/net/claw.c:68:
include/linux/fs.h:156:1: warning: this is the location of the previous definition

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>