open*(2) compat fixes (s390, arm64)

open*(2) compat fixes (s390, arm64)

The usual rules for open()/openat()/open_by_handle_at() are
 1) native 32bit - don't force O_LARGEFILE in flags
 2) native 64bit - force O_LARGEFILE in flags
 3) compat on 64bit host - as for native 32bit
 4) native 32bit ABI for 64bit system (mips/n32, x86/x32) - as for
    native 64bit

There are only two exceptions - s390 compat has open() forcing
O_LARGEFILE and arm64 compat has open_by_handle_at() doing the same
thing.  The same binaries on native host (s390/31 and arm resp.) will
*not* force O_LARGEFILE, so IMO both are emulation bugs.

Objections? The fix is obvious...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>