ide: tx4939ide: Fix the name used in a 'devm_request_mem_region()' call

This should be "tx4939ide" instead of "tx4938ide", but here MODNAME is even
better.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>