RDMA/mlx5: Remove MAYEXEC flag

MAYEXEC flag was mistakenly added in the commit cited in the fixes line.

Fixes: 4eb6ab13

 ("RDMA: Remove rdma_user_mmap_page")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>