[PATCH] Check return value of copy_to_user in compat_sys_pselect7

Fix

linux/fs/compat.c: In function compat_sys_pselect7
linux/fs/compat.c:1869: warning: ignoring return value of copy_to_user, declared with attribute warn_unused_result

To make it easier to handle I changed to semantics to not try to
write out a timespec if an error occurred. I hope that's ok.

Cc: dwmw2@infradead.org
Signed-off-by: Andi Kleen <ak@suse.de>