arch: um: Mock the _relaxed versions for read*/write*

This change adds mocks the _relaxed versions of the read/write{b,w,l,q}
functions for user-mode Linux (UML). This allows these to be used in
KUnit tests.

Change-Id: I78242f2a25b99fb6d73a6d7e0e6b1209572b7d4c
Signed-off-by: David Gow <davidgow@google.com>
Google-Bug-Id: 136604342
2 files changed