IB/uverbs: Add support to advise_mr

Add new ioctl method for the MR object - ADVISE_MR.

This command can be used by users to give an advice or directions to the
kernel about an address range that belongs to memory regions.

A new ib_device callback, advise_mr(), is introduced here to suupport the
new command. This command takes the following arguments:

- pd:		The protection domain to which all memory regions belong
- advice: 	The type of the advice
	  	* IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH - Pre-fetch a range of
		an on-demand paging MR
	  	* IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE - Pre-fetch a range
		of an on-demand paging MR with write intention
- flags:	The properties of the advice
		* IB_UVERBS_ADVISE_MR_FLAG_FLUSH - Operation must end before
		return to the caller
- sg_list:	The list of memory ranges
- num_sge:	The number of memory ranges in the list
- attrs:	More attributes to be parsed by the provider

Signed-off-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Guy Levi <guyle@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>