add type casting for uint64 parameter

[sangyun-han]

Add type casting for major.unix method. Its input parameter is uint64, but the parameter in unix.Stat_t is int32.

[cyphar]

You need to add a Signed-off-by: line to your commit(s) which indicates that you attest the Developer Certificate of Origin a statement about your contributions that you must read before signing (don't worry, it's quite short and easy-to-read). You can add it to your commits with git commit --amend -s, and then doing a git push --force.

[sangyun-han]

I added Signed-off-by.
Thank you for the comment.

[dqminh]

LGTM.

I believe this is only uint32 for MIPS though.

[cyphar]

Closing since #1824 was merged (which is basically the same thing). Thanks.