opus_pvq_search: Restore the proper use of conditional define and simplify the function name suffix handling.

Using named define properly documents the code paths.
It also avoids passing additional numbered arguments through
multiple levels of macro templates.

The suffix handling is done by concatenation, like in
other asm functions and avoid having two separate
"cglobal" defines.
Signed-off-by: Ivan Kalvachev <ikalvachev@gmail.com>