OMAP: SPI: Fix the trying to free nonexistent resource error

Currently there is a request_mem_region(r->start, ..
followed by r->start += pdata->regs_offset;

And then in remove

   r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
   release_mem_region(r->start, resource_size(r));

Here the offset addition is not taken care. Fix the code for the
same.

Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>