i2c: simtec: use release_mem_region instead of release_resource

Use api pair of request_mem_region and release_mem_region
instead of release_resource.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Anton Vasilyev <vasilyev@ispras.ru>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>