gianfar_ptp: use iomem, not ioports resource tree in probe

When using a 36 bit dtb file, the driver complains "resource busy".

Investigating the source of the message leads one to the
gianfar_ptp_probe function.

Since the type of the device resource requested in this function
is IORESOURCE_MEM, it should use "iomem_resource" instead of
"ioports_resource".

Signed-off-by: Wei Yang <Wei.Yang@windriver.com>
Cc: Claudiu Manoil <claudiu.manoil@freescale.com>
Cc: Timur Tabi <timur@freescale.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>