drivers/net/dc2114x.c: Fix compile warning

Fix this:
dc2114x.c: In function 'dc21x4x_initialize':
dc2114x.c:305:15: warning: assignment from incompatible pointer type

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Cc: Joe Hershberger <joe.hershberger@gmail.com>