eicon: fix define conflict with ptrace

eicon: fix define conflict with ptrace

* MODE_MASK is unused in eicon driver.
* Conflicts with a ptrace stuff on arm.

drivers/isdn/hardware/eicon/divasync.h:259:1: warning: "MODE_MASK" redefined
include2/asm/ptrace.h:48:1: warning: this is the location of the previous definition

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Karsten Keil <kkeil@suse.de>
Acked-by: Armin Schindler <armin@melware.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>