IB/uverbs: Fix command checking as part of ib_uverbs_ex_modify_qp()

IB/uverbs: Fix command checking as part of ib_uverbs_ex_modify_qp()

commit 05d14e7b0c138cb07ba30e464f47b39434f3fdef upstream.

If the input command length is larger than the kernel supports an error should
be returned in case the unsupported bytes are not cleared, instead of the
other way aroudn. This matches what all other callers of ib_is_udata_cleared
do and will avoid user ABI problems in the future.

Fixes: 189aba99e700 ("IB/uverbs: Extend modify_qp and support packet pacing")
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>