accel-ppp: fix qa issue 'found library in wrong location' while multilib enabled on qemux86-64

While multilib enabled on qemux86-64, accel-ppp-lib should be installed to
'${baselib}/accel-ppp', but the accel-ppp's CMakeLists.txt hardcoded
to install to 'lib/accel-ppp', such as:
...
INSTALL(TARGETS log_file
        LIBRARY DESTINATION lib/accel-ppp
)
...

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>