net: ti: icssg-prueth: Fix error cleanup on failing pruss_request_mem_region

We were just continuing in this case, surely not desired.

Fixes: 128d5874

 ("net: ti: icssg-prueth: Add ICSSG ethernet driver")
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>