IB/core: Make testing MR flags for writability a static inline function

IB/core: Make testing MR flags for writability a static inline function

BugLink: http://bugs.launchpad.net/bugs/1807469
commit 08bb558ac11ab944e0539e78619d7b4c356278bd upstream.

Make the MR writability flags check, which is performed in umem.c,
a static inline function in file ib_verbs.h

This allows the function to be used by low-level infiniband drivers.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>