Make flatview_extend_translation() take a MemTxAttrs argument

Make flatview_extend_translation() take a MemTxAttrs argument

As part of plumbing MemTxAttrs down to the IOMMU translate method,
add MemTxAttrs as an argument to flatview_extend_translation().
Its callers either have an attrs value to hand, or don't care
and can use MEMTXATTRS_UNSPECIFIED.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180521140402.23318-7-peter.maydell@linaro.org