lpm: install vector header files with meson

lpm: install vector header files with meson

The main rte_lpm.h header file also includes architecture specific headers,
depending on the architecture on which it is used. These also need to be
installed into the include directory as part of the "ninja install"
process. Thankfully, since the vector headers all have different names we
can just install all 3 of them in all cases, which avoids conflicts or
issues with multi-architecture installs, or the need to use
architecture-specific subdirectories.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: Luca Boccassi <bluca@debian.org>