smb.h: do not include linux/time.h in userspace

linux/time.h conflicts with time.h from glibc

It breaks building smbmount from samba.  It's regression introduced by
commit 76308da1

 (" smb.h: uses struct timespec but didn't include
linux/time.h").

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: <stable@kernel.org>             [2.6.26.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>