Fixed kernel crash when running devinfo

When calling to ib_uverbs_cleanup_ucontext, there is a call to
mutex_lock of xrcd_table_mutex, which was not initialized.
Added missing initialization for xrcd_table_mutex.

Signed-off-by: Orit Moskovich <oritm@mellanox.com>
Enable ib_dev.mmap function

Removed the ifdef linux from this function.
Added stub function for contiguous pages to avoid compilation
errors.

Signed-off-by: Orit Moskovich <oritm@mellanox.com>