gpu: ion: IOCTL return success when error occurs

ION_IOC_MAP, ION_IOC_SHARE, and ION_IOC_IMPORT may return
success when an error occurs.

Add correct error handling to ION_IOC_MAP, ION_IOC_SHARE, and
ION_IOC_IMPORT.

Change-Id: I61c6b0c574da425604235b2d39e13e4a27f7b6f3
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>