[PATCH] x86_64: fix put_user for 64-bit constant

On x86-64, a put_user call using a 64-bit pointer and a constant value that
is > 0xffffffff will produce code that doesn't assemble.  This patch fixes
the asm construct to use the Z constraint for 32-bit constants.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>