target/arm: Provide and use H8 and H1_8 macros

Currently we provide Hn and H1_n macros for accessing the correct
data within arrays of vector elements of size 1, 2 and 4, accounting
for host endianness.  We don't provide any macros for elements of
size 8 because there the host endianness doesn't matter.  However,
this does result in awkwardness where we need to pass empty arguments
to macros, because checkpatch complains about them.  The empty
argument is a little confusing for humans to read as well.

Add H8() and H1_8() macros and use them where we were previously
passing empty arguments to macros.

Suggested-by: Richard Henderson <[email protected]>
Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-id: [email protected]
Message-id: [email protected]