[stable 4.9-4.19] Fix arm64 build regression in xen-netback

[Ben Hutchings <ben@decadent.org.uk>]

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The arm64 implementations of some atomic operations had incorrect
assembly constraints.  Depending on the compiler version and
options, this can result in a build failure for some parameter
values:

/tmp/ccDOb5nB.s: Assembler messages:
/tmp/ccDOb5nB.s:2214: Error: immediate out of range at operand 3 -- `bic w1,w0,5'

This has specifically been seen when building a 4.9 stable kernel with
gcc 6.3.0, since commit 23025393dbeb "xen/netback: use lateeoi irq
binding" was applied.  I can also reproduce it with 4.14.

I cannot reproduce it with 4.19, but the same fixes are applicable and
the issue presumably could occur when using different compiler
options.

I haven't done anything about the 4.4 branch since it does not have
that xen-netback fix and it has significantly different definitions
for arm64 atomic ops.

I've attached a mailbox of patches for each of the 4.9, 4.14, and 4.19
branches.

Ben.

-- 
Ben Hutchings
I'm always amazed by the number of people who take up solipsism because
they heard someone else explain it. - E*Borg on alt.fan.pratchett

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